Polythionic Acid (PTA) Composition for Preventing Stress Corrosion Cracking in 300 Series Stainless Steel and Method of Using the Same

Abstract

A composition, system, and method for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking are disclosed. The composition comprises a pre-mixed K2CO3 treatment solution that can be diluted to a desired concentration of K2CO3 by in-tube mixing before being placed in the treated stainless steel vessel.

Description

Technology Field

[0001] The present invention relates to a polythionic acid composition for preventing stress corrosion cracking in 300 series stainless steel and a method of using the same. More specifically, the present invention relates to a pre-mixed solution that can be diluted on-site and used to treat austenitic stainless steel or austenitic alloys for preventing stress corrosion cracking.

[0002] <Cross-reference to related applications>

[0003] This application claims priority to U.S. provisional application No. 63 / 191,058 filed on May 20, 2021, the entire contents of which are incorporated herein by reference. Background Technology

[0004] Historically, to prevent polythionic acid stress cracking, operators have treated stainless steel vessels with soda ash (i.e., sodium carbonate, Na2CO3). In such cases, a large-capacity steel tank (e.g., a Frac tank) containing clean water with hundreds of pounds of dry soda ash is used. The soda ash and water are mixed in the tank to form a treatment solution. The tank is then placed "upstream" of the stainless steel vessel requiring treatment.

[0005] The treatment solution is injected into the bottom of the stainless steel equipment to be treated until it is full, and once full, the solution exits the top of the container and is pumped back into a large-capacity tank. This mixture-injection-return circulation process is performed in a closed loop.

[0006] When the treatment solution is returned to the large-capacity tank, the operator measures the pH of the solution. Based on the measured pH, the operator can determine whether the treatment process is effective. If the measurement result shows a pH level below 9, the closed-loop circulation application must be continued while adding more soda ash to raise the pH level. If the measurement value is greater than 9 and the closed-loop application process can be terminated after at least 2 hours, the treated tank can be drained and the pumping equipment can be disconnected from the treated tank. The closed-loop circulation approach is governed by three main realities.

[0007] First, continuous circulation of the treatment solution is necessary. Otherwise, the solubility of soda ash within the solution will be limited, causing the soda ash to precipitate and fall out of the solution.

[0008] Second, according to the NACE international standard, in cases where there is no clean equipment and surrounding piping (i.e., where petroleum contaminants such as sludge deposits and fouling are present), treatment is performed in a circulating manner (Reference: NACE SP0170-2018, Item No. 21002, Approved Date 2018-09-10, ISBN 1-57590-039-4). Specifically, according to the NACE international standard, 1) all equipment to be treated must be filled with a soda ash-containing treatment solution in an inert atmosphere to minimize oxygen contamination, 2) the equipment must be treated with the treatment solution through active circulation for at least 2 hours, and 3) the circulating treatment solution must be analyzed at appropriate intervals to maintain pH and chloride limits.

[0009] Third, the effectiveness of the treatment process can only be verified by testing the soda ash-containing treatment solution 'before' and 'after'. In other words, the operator must measure the pH of the solution by comparing the pH readings before and after the solution is transferred to the treatment container. To obtain these comparative measurements, the operator must circulate within a closed loop. Furthermore, due to these measurement and testing requirements, it is impossible to even consider a one-time application. The problem to be solved

[0010] Due to the operational realities and requirements mentioned above, the permanent circulation within a closed loop has long been established as a persistent and fixed concept in oil refineries. means of solving the problem

[0011] A system for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking according to various embodiments of the present disclosure comprises: a storage container configured to store a pre-mixed K2CO3 treatment solution and fluidly coupled to a first conduit; a water source fluidly coupled to a second conduit; a third conduit fluidly coupled to each of the first conduit, the second conduit, and the stainless steel vessel to be treated; and a waste container fluidly coupled to the stainless steel vessel; wherein, when the system is used, the pre-mixed K2CO3 treatment solution is transferred from the storage container to the third conduit through the first conduit, and water is transferred from the water source to the third conduit through the second conduit, and the pre-mixed K2CO3 treatment solution and water are mixed in the third conduit to form a diluted K2CO3 treatment solution, and the diluted K2CO3 treatment solution is transferred to the stainless steel vessel through the third conduit. In some cases, the first conduit further includes an injection pump. In some cases, the first conduit further includes an injection flow control valve. In some cases, the first conduit further includes an injection pump and an injection flow control valve. In some cases, the second conduit further includes a water injection flow control valve. In some cases, the second conduit further includes a flow meter. In some cases, the second conduit further includes a water injection flow control valve and a flow meter.In some cases, the storage container has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about 1040g per liter of water, alternatively per liter of water The system is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of about 900g to about 1020g, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water. In some cases, the system is configured to produce a diluted K2CO3 treatment solution containing about 0.1 to about 10 w / w% K2CO3, alternatively about 0.25 to about 8 w / w% K2CO3, alternatively about 0.5 to about 7 w / w% K2CO3, alternatively about 0.75 to about 6 w / w% K2CO3, alternatively about 1 to about 5 w / w% K2CO3, or alternatively about 1 to about 2 w / w% K2CO3.

[0012] Other systems for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking according to various embodiments of the present disclosure include: a storage container configured to store a pre-mixed K2CO3 treatment solution and fluidly coupled to a first conduit; a water source fluidly coupled to a second conduit; an eductor coupled to each of the first conduit and the second conduit; and a third conduit fluidly coupled to the stainless steel vessel to be treated and the eductor, respectively. And, the system includes a waste container fluidly coupled to the stainless steel container, wherein when the system is in use, a pre-mixed K2CO3 treatment solution is transferred from the storage container to the eductor through the first conduit, and water is transferred from the water source to the eductor through the second conduit, and the pre-mixed K2CO3 treatment solution and water are mixed in the eductor to form a diluted K2CO3 treatment solution, and the diluted K2CO3 treatment solution is transferred from the eductor to the stainless steel container through the third conduit. In some cases, the first conduit further includes an injection flow control valve. In some cases, the second conduit further includes a water injection flow control valve. In some cases, the second conduit further includes a flow meter. In some cases, the second conduit further includes a water injection flow control valve and a flow meter.In some cases, the storage container has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about 1040g per liter of water, alternatively per liter of water The system is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of about 900g to about 1020g, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water. In some cases, the system is configured to produce a diluted K2CO3 treatment solution containing about 0.1 to about 10 w / w% K2CO3, alternatively about 0.25 to about 8 w / w% K2CO3, alternatively about 0.5 to about 7 w / w% K2CO3, alternatively about 0.75 to about 6 w / w% K2CO3, alternatively about 1 to about 5 w / w% K2CO3, or alternatively about 1 to about 2 w / w% K2CO3.

[0013] According to various embodiments of the present disclosure, a method for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking comprises: incorporating the stainless steel vessel into a system according to various embodiments of the present disclosure; injecting the diluted K2CO3 treatment solution into the stainless steel vessel until the stainless steel vessel is filled or substantially filled with the diluted K2CO3 treatment solution; maintaining the diluted K2CO3 treatment solution in the stainless steel vessel for a certain period of time; and removing the diluted K2CO3 treatment solution from the stainless steel vessel. In some cases, the diluted K2CO3 treatment solution is removed from the stainless steel vessel to a waste container. In some cases, the certain period of time is at least 2 hours. In some cases, the step of maintaining the diluted K2CO3 treatment solution in the stainless steel vessel for a certain period of time is performed at a temperature of up to 50°C. In some cases, the step of injecting the diluted K2CO3 treatment solution into the stainless steel vessel until the stainless steel vessel is filled or substantially filled with the diluted K2CO3 treatment solution is performed in an inert atmosphere. In some cases, the step of maintaining the diluted K2CO3 treatment solution in the stainless steel container for a certain period of time further includes measuring the pH of the contents within the stainless steel container, wherein the contents include the diluted K2CO3 treatment solution.

[0014] A first embodiment of the present disclosure is a system for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking, the system comprising: a storage container configured to store a pre-mixed K2CO3 treatment solution and fluidly connected to a first conduit; a water source fluidly connected to a second conduit; a third conduit fluidly connected to each of the first conduit, the second conduit, and the stainless steel vessel to be treated; and a waste container fluidly connected to the stainless steel vessel, wherein when the system is used, the pre-mixed K2CO3 treatment solution is transferred from the storage container to the third conduit through the first conduit, water is transferred from the water source to the third conduit through the second conduit, the pre-mixed K2CO3 treatment solution and water are mixed in the third conduit to form a diluted K2CO3 treatment solution, and the diluted K2CO3 treatment solution can be transferred to the stainless steel through the third conduit.

[0015] A second embodiment of the present disclosure is a system according to the first embodiment in which the first conduit further comprises an injection pump.

[0016] A third embodiment of the present disclosure is a system according to the first embodiment or the second embodiment, wherein the first conduit further comprises an injection flow control valve.

[0017] The fourth embodiment of the present disclosure is a system according to any one of the first to third embodiments, wherein the first conduit further comprises an injection pump and an injection flow control valve.

[0018] The fifth embodiment of the present disclosure is a system according to any one of the first to fourth embodiments, wherein the second conduit further comprises a water injection flow control valve.

[0019] The sixth embodiment of the present disclosure is a system according to any one of the first to fifth embodiments, wherein the second conduit further comprises a flow meter.

[0020] The seventh embodiment of the present disclosure is a system according to any one of the first to sixth embodiments, wherein the second conduit further comprises a water injection flow control valve and a flow meter.

[0021] The eighth embodiment of the present disclosure is a system according to any one of the first to seventh embodiments, wherein the storage container has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about It is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of 1040g, alternatively a K2CO3 concentration of about 900g to about 1020g per liter of water, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water.

[0022] The ninth embodiment of the present disclosure is a system according to any one of the first to eighth embodiments, wherein the system is configured to produce a diluted K2CO3 treatment solution containing about 0.1 to about 10 w / w% K2CO3, alternatively about 0.25 to about 8 w / w% K2CO3, alternatively about 0.5 to about 7 w / w% K2CO3, alternatively about 0.75 to about 6 w / w% K2CO3, alternatively about 1 to about 5 w / w% K2CO3, and alternatively about 1 to about 2 w / w% K2CO3.

[0023] The tenth embodiment of the present disclosure is a system for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking, the system comprising: a storage container configured to store a pre-mixed K2CO3 treatment solution and fluidly coupled to a first conduit; a water source fluidly coupled to a second conduit; an eductor coupled to each of the first conduit and the second conduit; and a third conduit fluidly coupled to the stainless steel vessel to be treated and the eductor, respectively. And, the system includes a waste container coupled to the stainless steel container so as to be fluidly connected, and when the system is used, the pre-mixed K2CO3 treatment solution is transferred from the storage container to the eductor through the first conduit, and water is transferred from the water source to the eductor through the second conduit, and the pre-mixed K2CO3 treatment solution and water are mixed in the eductor to form a diluted K2CO3 treatment solution, and the diluted K2CO3 treatment solution is transferred from the eductor to the stainless steel container through the third conduit.

[0024] The 11th embodiment of the present disclosure is a system according to the 10th embodiment, and the first conduit further includes an injection flow control valve.

[0025] The 12th embodiment of the present disclosure is a system according to the 10th embodiment or the 11th embodiment, and the second conduit further includes a water injection flow control valve.

[0026] The 13th embodiment of the present disclosure is a system according to any one of the 10th to 12th embodiments, and the second conduit further includes a flow meter.

[0027] The 14th embodiment of the present disclosure is a system according to any one of the 10th to 13th embodiments, and the second conduit further includes a water injection flow control valve and a flow meter.

[0028] The 15th embodiment of the present disclosure is a system according to any one of the 10th to 14th embodiments, wherein the storage container has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about It is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of 1040g, alternatively a K2CO3 concentration of about 900g to about 1020g per liter of water, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water.

[0029] The 16th embodiment of the present disclosure is a system according to any one of the 10th to 15th embodiments, wherein the system is configured to produce a diluted K2CO3 treatment solution containing about 0.1 to about 10 w / w% K2CO3, alternatively about 0.25 to about 8 w / w% K2CO3, alternatively about 0.5 to about 7 w / w% K2CO3, alternatively about 0.75 to about 6 w / w% K2CO3, alternatively about 1 to about 5 w / w% K2CO3, and alternatively about 1 to about 2 w / w% K2CO3.

[0030] The 17th embodiment of the present disclosure is a method for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking, the method comprising: a) incorporating a stainless steel vessel into a system according to any one of the 1st to 16th embodiments; b) injecting a diluted K2CO3 treatment solution into the stainless steel vessel until the stainless steel vessel is filled with or substantially filled with the diluted K2CO3 treatment solution; c) maintaining the diluted K2CO3 treatment solution in the stainless steel vessel for a certain period of time; and d) removing the diluted K2CO3 treatment solution from the stainless steel vessel.

[0031] The 18th embodiment of the present disclosure is a method according to the 17th embodiment, wherein the diluted K2CO3 treatment solution is removed from the stainless steel container to the waste container.

[0032] The 19th embodiment of the present disclosure is a method according to the 17th embodiment or the 18th embodiment, and the constant time is at least 2 hours.

[0033] The 20th embodiment of the present disclosure is a method according to any one of the 17th to 19th embodiments, and step c) is performed at a temperature of up to 50°C.

[0034] The 21st embodiment of the present disclosure is a method according to any one of the 17th to 20th embodiments, wherein step b) is performed under an inert atmosphere.

[0035] The 22nd embodiment of the present disclosure is a method according to any one of the 17th to 21st embodiments, wherein step c) further comprises measuring the pH of the contents in the stainless steel container, and the contents include the diluted K2CO3 treatment solution. Brief explanation of the drawing

[0036] Figure 1 is a schematic diagram of a conventional technology system for treating stainless steel vessels to protect them from stress corrosion cracking. FIG. 2 is a schematic diagram of a system according to various embodiments of the present disclosure for treatment and protection from stress corrosion cracking. FIG. 3 is a schematic diagram of another system according to various embodiments of the present disclosure for treatment and protection from stress corrosion cracking. FIG. 4 is a flowchart of a method according to various embodiments of the present disclosure for treatment and protection from stress corrosion cracking. FIG. 5 is a flowchart of another method according to various embodiments of the present disclosure for treatment and protection from stress corrosion cracking. Specific details for implementing the invention

[0037] The following description of the embodiments is by nature merely illustrative and is not intended to limit the subject matter, application, or use of the present disclosure.

[0038] As used generally, the range is used as an abbreviation to describe each and all values ​​within the range. All values ​​within the range may be selected as the end of the range. Unless otherwise specified, all percentages (%) and amounts expressed in this specification and elsewhere in this specification should be understood as representing percentages by weight (wt%).

[0039] For the purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing quantities, percentages or ratios and other figures used in this specification and claims shall be understood to be modified in all cases by the term “approximately.” The use of the term “approximately” applies to all numeric values, whether or not explicitly indicated. This term generally refers to a range of numbers that a person skilled in the art would consider to be a reasonable deviation from the stated numeric value (i.e., having equivalent function or result). For example, this term may be interpreted to include deviations of ±10%, ±5%, ±1%, ±0.5%, and ±0.1% of a given numeric value, provided that such deviation does not alter the function or result of the figure. Accordingly, unless otherwise specified, the numeric parameters presented in this specification and the appended claims are approximations that may vary depending on the desired characteristics to be obtained by the present invention.

[0040] As used in this specification and the appended claims, the singular form includes the plural form unless explicitly and clearly limited to a single object. As used in this specification, the term “include” and its grammatical variations mean that the reference to an item in the list is non-restrictive so as not to exclude other similar items that may replace or add to the listed item. For example, the terms "include" (also grammatical variations such as "including" and "including"), "have" (also grammatical variations such as "having" and "having"), and "have" (also grammatical variations such as "having" and "having") as used in this specification and the following claims are inclusive (i.e., open) and do not exclude additional elements or steps. Accordingly, these terms may include not only the mentioned element(s) or step(s) but also other elements or steps not explicitly mentioned. Furthermore, in this specification, the reference to an element without singular or plural not specified may mean "one," but is also consistent with the meanings of "one or more," "at least one," and "one or more than one." Accordingly, the reference to an element without singular or plural not specified does not exclude the existence of additional identical elements without further restriction.

[0041] For the purposes of this specification and the appended claims, the term “coupled” means the linking or connection of two objects. The linking may be permanent or reversible. The linking may be direct or indirect. Indirect linking includes connecting or joining two objects through one or more intermediaries. As used herein, the term “substantially” is defined as essentially corresponding to a particular dimension, shape, or other word that is substantially modified so that the components do not need to be exactly the same. For example, “substantially cylindrical” means that an object resembles a cylinder but may have one or more deviations from an actual cylinder.

[0042] According to various embodiments of the present disclosure, a method for protecting austenitic stainless steel or austenitic alloy refinery equipment from stress corrosion cracking with polythionic acid during shutdown operations is described herein. The method according to various embodiments of the present disclosure can protect said refinery equipment from stress corrosion cracking without the need to apply a treatment solution through a closed-loop circulation approach.

[0043] FIG. 1 is a schematic diagram illustrating a conventional system (100) for treating a stainless steel vessel with a soda ash treatment solution to protect the vessel from stress corrosion cracking, wherein the soda ash treatment solution is produced on-site. In practice, the soda ash treatment solution cannot be produced outside the site due to the limited soda ash solubility in water (approximately 212.5 g / L at 20°C; or a 17.5 wt% soda ash saturated solution at room temperature), and thousands of gallons of treatment solution are required to treat the stainless steel vessel, and fresh soda ash must be continuously added to the treatment solution during the treatment process. The system (100) includes a treatment solution storage vessel (110) and a vessel (170) joined together in a closed-loop form. The vessel (170) includes an inner surface that may be damaged over time due to polythionic acid stress corrosion cracking. Water is supplied to the container (110) from the source (120) through the conduit (130). Soda ash is supplied to the container (110) from the soda ash source (140). The soda ash source (140) is generally a soda ash containing means such as a hopper, bag, drum, etc. The soda ash is supplied to the container (110) from the soda ash source (140) in an automated manner under the control of an operator or manually by an operator. The soda ash and water are mixed in the container (110) so that the resulting soda ash treatment solution contains 1 to 5 weight percent of soda ash and has a pH greater than 9. The container (110) may further include an internal or external heating element and / or means (means for stirring or agitating the contents of the container (110) to help prepare the soda ash treatment solution within the container (110) and to promote the continuous dissolution of soda ash in water).

[0044] Once formed, the soda ash treatment solution is transferred from the container (110) to the bottom of the contaminated container (170) through the pump (150) and conduits (160, 180). The soda ash treatment solution is injected into the container (170) to fill the container (170) while maintaining the contaminated container (170) in an inert atmosphere. The injection of the treatment solution into the contaminated container (170) continues so that the treatment solution exits the top of the container (170) and is transferred back to the container (110) through the conduit (190). In this closed-loop structure, the treatment solution is actively circulated through the container (170) for at least 2 hours. During circulation, the treatment solution is analyzed periodically to check whether the pH and chloride limit of the solution are maintained. Generally, the treatment solution is analyzed before re-entering the container (110) and before being transferred from the container (110) to the contaminated container (170). In most cases, additional soda ash must be added to the treatment solution from the soda ash source (140) to maintain the essential properties of the treatment solution.

[0045] Unlike the use of soda ash in the prior art, the present disclosure relates to the use of K2CO3. According to various embodiments of the present disclosure, the K2CO3 treatment solution is provided as a pre-mixed solution, thus eliminating the need to prepare the treatment solution on-site in a container. Unlike soda ash (212.5 g / L), which has limited solubility in water under ambient conditions, K2CO3 has a solubility (1120 g / L at 20°C) that allows for the preparation of a highly concentrated pre-mixed solution (up to about 52.8 wt% K2CO3 at 20°C). In some cases, the pre-mixed K2CO3 treatment solution is a saturated solution. In some cases, the pre-mixed K2CO3 treatment solution contains a K2CO3 concentration of about 100 g to about 1120 g per liter of water. In other cases, the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about 1040g per liter of water, alternatively water It is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of about 900g to about 1020g per liter of water, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water. Preferably, the pre-mixed K2CO3 treatment solution contains about 49% by weight of K2CO3.

[0046] In some cases, a diluted form of a concentrated pre-mixed K2CO3 treatment solution according to various embodiments of the present disclosure may be mixed with one or more corrosion inhibitors to reduce the likelihood of chloride stress corrosion cracking. When one or more corrosion inhibitors are used, the diluted form of the concentrated pre-mixed K2CO3 treatment solution used as described in the method below must contain a sufficient amount of corrosion inhibitor when the treatment solution is diluted as described herein. The diluted solution contains about 0.1 to about 1 weight%, preferably about 0.2 to about 0.8 weight%, more preferably about 0.25 to about 0.6 weight%, even more preferably about 0.3 to about 0.5 weight%, and more preferably about 0.4 weight% of corrosion inhibitor. In some cases, one or more corrosion inhibitors may include sodium nitrate.

[0047] FIG. 2 is a schematic diagram illustrating a system (200) according to various embodiments for treating and protecting a vessel from stress corrosion cracking, wherein the K2CO3 treatment solution is provided as a pre-mixed solution. In some cases, the pre-mixed K2CO3 treatment solution is a saturated solution. In some cases, the pre-mixed K2CO3 treatment solution contains a K2CO3 concentration of about 100 g to about 1120 g per liter of water. In other cases, the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about 1040g per liter of water, alternatively water The system is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of about 900g to about 1020g per liter of water, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water. Preferably, the pre-mixed K2CO3 treatment solution contains about 49% by weight of K2CO3. The system (200) generally includes a storage container (210) for the pre-mixed K2CO3 treatment solution, a water source (220), a vessel (230), and a waste vessel (240).Water is delivered from a water source (220) through a conduit (255, 265) at a controlled flow rate controlled by a water rate control valve (270). The flow rate of water delivered through the conduit (255) can be monitored using a flow meter (280) connected to the conduit (255). A container (210) is connected to an injection pump (250) through a conduit (215). The type of pump used as the injection pump (250) is not limited to a specific type of pump. A pre-mixed K2CO3 treatment solution is pumped through a conduit (225) to an injection rate control valve (260). The injection rate control valve (260) can be operated to control the amount of concentrated K2CO3 treatment solution delivered to the conduit (265) through a conduit (235). A diluted K2CO3 treatment solution is formed by mixing water and a concentrated K2CO3 treatment solution within a conduit (265) that occurs at the intersection of conduit (235) and conduit (255). The diluted K2CO3 treatment solution is delivered through the conduit (265) to the inlet (not shown) of a container (230). Subsequently, the diluted K2CO3 treatment solution is pumped into the container (230) until the container is filled with the diluted K2CO3 treatment solution and soaked for a certain period of time. After a certain period of time has elapsed, the used diluted K2CO3 treatment solution is transferred to a waste container (240) via the conduit (275), which is connected to the outlet (not shown) of the container (230) and the inlet (not shown) of the container (240). In some cases, the outlet of the container (230) is located at the bottom or bottom portion of the container (230), and the outlet is located at the top or upper portion of the container (230). In some cases, the inlet of the container (230) is located at the top or upper portion of the container (230), and the outlet is located at the bottom or lower portion of the container (230).

[0048] In the system (200), one or more corrosion inhibitors may be included in the diluted K2CO3 treatment solution, wherein the diluted K2CO3 treatment solution contains about 0.1 to about 1 weight%, preferably about 0.2 to about 0.8 weight%, more preferably about 0.25 to about 0.6 weight%, even more preferably about 0.3 to about 0.5 weight%, and even more preferably about 0.4 weight% of the corrosion inhibitor. In some cases, one or more corrosion inhibitors may be added to water from a water source (220). In some cases, one or more corrosion inhibitors may be added to the diluted K2CO3 treatment solution in the conduit (265). In some cases, one or more corrosion inhibitors may be added to the K2CO3 treatment solution in the container (230).

[0049] FIG. 3 is a schematic diagram illustrating another system (300) according to various embodiments of the present disclosure for treating and protecting a vessel from stress corrosion cracking, wherein the K2CO3 treatment solution is provided as a pre-mixed solution. In some cases, the pre-mixed K2CO3 treatment solution is a saturated solution. In some cases, the pre-mixed K2CO3 treatment solution contains a K2CO3 concentration of about 100 g to about 1120 g per liter of water. In other cases, the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about 1040g per liter of water, alternatively water The system is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of about 900g to about 1020g per liter of water, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water. Preferably, the pre-mixed K2CO3 treatment solution contains about 49% by weight of K2CO3. The system (300) generally includes a pre-mixed K2CO3 treatment solution storage container (310), a water source (320), a container (330), and a waste container (340). Water is delivered from a water source (320) to an eductor (380) through conduits (335, 345) at a controlled flow rate controlled by a water flow control valve (360).The flow rate of water delivered through the conduit (345) can be monitored using a flow meter (370) connected to the conduit (345). The container (310) is connected to an injection flow control valve (350) through the conduit (315). The concentrated pre-mixed K2CO3 treatment solution is delivered to the eductor (380) through the conduit (325). Inside the eductor (380), the mixture of water and the pre-mixed K2CO3 treatment solution forms a diluted K2CO3 treatment solution. The diluted K2CO3 treatment solution is delivered to the inlet (not shown) of the container (330) through the conduit (365). Subsequently, the diluted K2CO3 treatment solution is pumped into the container (330) until the container is filled with the diluted K2CO3 treatment solution and immersed for a certain period of time. After a certain period of time has elapsed, the used diluted K2CO3 treatment solution is transferred to a waste container (340) via a conduit (375), which is connected to an outlet (not shown) of a container (330) and an inlet (not shown) of a container (340). In some cases, the outlet of the container (330) contaminated with petroleum is located at the bottom or bottom portion of the container (330), and the outlet is located at the top or upper portion of the container (330). In some cases, the inlet of the container (330) is located at the top or upper portion of the container (330), and the outlet is located at the bottom or lower portion of the container (330).

[0050] In the system (300), one or more corrosion inhibitors may be included in the diluted K2CO3 treatment solution, wherein the diluted K2CO3 treatment solution contains about 0.1 to about 1 weight%, preferably about 0.2 to about 0.8 weight%, more preferably about 0.25 to about 0.6 weight%, even more preferably about 0.3 to about 0.5 weight%, and even more preferably about 0.4 weight% of the corrosion inhibitor. In some cases, one or more corrosion inhibitors may be added to water from a water source (220). In some cases, one or more corrosion inhibitors may be added to the diluted K2CO3 treatment solution in the conduit (365). In some cases, one or more corrosion inhibitors may be added to the K2CO3 treatment solution in the container (330).

[0051] An exemplary method (400) for treating a stainless steel vessel with a K2CO3 treatment solution to protect the vessel from stress corrosion cracking during a shutdown operation using a system (200) is schematically illustrated in FIG. 4. As illustrated in FIG. 4, the method (400) may proceed according to the following method steps. A person skilled in the art will understand that, without going beyond the scope of the method, in the process of treating a stainless steel vessel with a K2CO3 treatment solution to protect the vessel from stress corrosion cracking, one or more steps of the method (400) may be omitted and / or one or more steps may be added, and one or more elements of the system (200) may generally be added or omitted. In some cases, the method (400) may begin at step 410.

[0052] In step 410, a stainless steel container (230) is integrated into the system (200) to treat and protect the container (230) from stress corrosion cracking. The container is integrated into the system (200) by connecting the fluid inlet of the container (230) to a conduit (265) to contain the K2CO3 treatment solution inside, and connecting the fluid outlet of the container (230) to a conduit (275) to discharge the used K2CO3 treatment solution from the container (230) to a waste container (240) after the immersion step described below. After step 410 is completed, the method (400) can proceed to step 420.

[0053] In step 420, a K2CO3 treatment solution storage container (210) containing a pre-mixed K2CO3 solution is connected to a conduit (215), and a water supply source (220) is connected to a conduit (245). The type of container (210) used to store the pre-mixed K2CO3 treatment solution is not particularly limited. A container capable of storing a basic (i.e., pH >7) solution for a long period is suitable. In some cases, the pre-mixed K2CO3 treatment solution in the storage container (210) is a saturated solution. In some cases, the pre-mixed K2CO3 treatment solution contains a K2CO3 concentration of about 100g to about 1120g of K2CO3 per liter of water. In other cases, the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about 1040g per liter of water, alternatively water It is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of about 900g to about 1020g per liter of water, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water. Preferably, the pre-mixed K2CO3 treatment solution contains about 49% by weight of K2CO3.In order to minimize the amount of pre-mixed K2CO3 treatment solution required for a specific treatment and protection process and the amount of raw product delivered to the container, and to reduce the number of times the storage container (210) must be replaced during a single treatment and protection process, it is desirable to use a pre-mixed K2CO3 treatment solution having a concentration as high as feasible, taking into account environmental and / or process considerations such as ambient air temperature or the degree or type of petroleum contamination within the container (230).

[0054] In some cases, step 420 may be performed before step 410. In some cases, step 410 and step 420 are performed simultaneously. After step 420 is completed, the method (400) may proceed to step 430.

[0055] In step 430, a controlled amount of pre-mixed K2CO3 treatment solution is transferred from the storage container (210) to the conduit (265) through the conduit (215, 225, 235), pump (250), and injection flow control valve (260). Also in step 430, a controlled amount of water, monitored by the flow meter (280), is transferred from the water source (220) to the conduit (265) through the conduit (245, 255) and injection flow control valve (270). The pre-mixed K2CO3 treatment solution and water are mixed directly in the conduit (265) to form a diluted K2CO3 treatment solution. The pre-mixed K2CO3 treatment solution and water must be delivered into the conduit (265) in relative amounts such that the resulting diluted K2CO3 treatment solution contains about 0.1 to about 10 w / w% K2CO3, preferably about 0.25 to about 8 w / w% K2CO3, more preferably about 0.5 to about 7 w / w% K2CO3, even more preferably about 0.75 to about 6 w / w% K2CO3, and even more preferably about 1 to about 5 w / w% K2CO3. In some cases, a diluted K2CO3 treatment solution containing about 1 to about 2 w / w% K2CO3 is formed. After step 430 is completed, the method (400) may proceed to step 440.

[0056] In step 440, the diluted K2CO3 treatment solution is injected into the stainless steel container (230) through the fluid inlet of the container (230) to which the conduit (265) is connected. The diluted K2CO3 treatment solution is injected into the stainless steel container (230) until the container (230) is filled or substantially filled with the diluted K2CO3 treatment solution. The container (230) is filled or substantially filled under an inert atmosphere to minimize oxygen contamination. After step 440 is completed, the method (400) may proceed to step 450.

[0057] In step 450, the diluted K2CO3 treatment solution is maintained in a stainless steel container (230) for a certain period of time to allow petroleum contaminants to penetrate into the treatment solution. In some cases, this "soak" step is performed at room temperature. In some cases, this soak step is performed at a high temperature of up to about 50°C. Generally, the certain period is at least 2 hours. During step 450, the pH of the contents of the stainless steel container is measured. pH measurements can be performed continuously or incrementally over time. Optionally, other chemical analyses, such as petroleum contaminant and / or chloride content, can also be performed during step 450. After step 450 is completed, the method (400) can proceed to step 460.

[0058] In step 460, the used diluted K2CO3 treatment solution exits the container (230) through the fluid outlet and is disposed of in the waste container (240), and after this is completed, the K2CO3 A residual film must remain on the inner surface of the vessel (230) during a downtime period to ensure continuous protection from stress corrosion cracking. After step 460 is completed, the method (400) can proceed to step 470.

[0059] In step 470, steps 410 through 460 may be repeated one or more times until it is confirmed that the container (230) no longer contains petroleum contaminants, depending on the pH and optional chemical analysis performed in step 450. At the end of step 470, the method (400) is terminated.

[0060] In some cases, one or more corrosion inhibitors described in this specification may be added in any one of steps 430 to 450.

[0061] An exemplary method (500) for treating a stainless steel vessel with a K2CO3 treatment solution to protect the vessel from stress corrosion cracking using a system (300) is schematically illustrated in FIG. 5. The method (500) may proceed according to the following method steps. It will be understood that, without going outside the scope of the method, in the process of treating a stainless steel vessel with a K2CO3 treatment solution to protect the vessel from stress corrosion cracking, one or more steps of the method (500) may be omitted and / or one or more steps may be added, and one or more elements of the system (300) may generally be added or omitted. In some cases, the method (500) may begin at step 510.

[0062] In step 510, a stainless steel container (330) is integrated into the system (300) to treat and protect the container (330) from stress corrosion cracking. The container (330) is integrated into the system (300) by connecting the fluid inlet of the container (300) to a conduit (365) to contain the K2CO3 treatment solution therein, and by connecting the fluid outlet of the fluid container (330) to a conduit (375) to discharge the K2CO3 treatment solution from the container (330) to a waste container (340) after the immersion step described below.

[0063] In step 520, a K2CO3 treatment solution storage container (310) is connected to a conduit (315), and a water supply source (320) is connected to a conduit (335). The type of container used to store the pre-mixed concentrated K2CO3 treatment solution is not particularly limited. A container capable of storing a basic (i.e., pH >7) solution for a long period is suitable. In some cases, the pre-mixed K2CO3 treatment solution in the storage container (310) is a saturated solution. In some cases, the pre-mixed K2CO3 treatment solution contains a K2CO3 concentration of about 100g to about 1120g of K2CO3 per liter of water. In other cases, the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of about 200g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 300g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 400g to about 1120g per liter of water, alternatively a K2CO3 concentration of about 500g to about 1100g per liter of water, alternatively a K2CO3 concentration of about 600g to about 1080g per liter of water, alternatively a K2CO3 concentration of about 700g to about 1060g per liter of water, alternatively a K2CO3 concentration of about 800g to about 1040g per liter of water, alternatively water It is configured to store a pre-mixed K2CO3 treatment solution having a K2CO3 concentration of about 900g to about 1020g per liter of water, alternatively a K2CO3 concentration of about 920g to about 1000g per liter of water, or alternatively a K2CO3 concentration of about 940g to about 980g per liter of water. Preferably, the pre-mixed K2CO3 treatment solution contains about 49% by weight of K2CO3.In order to minimize the amount of pre-mixed K2CO3 treatment solution required for a specific treatment and protection process and the amount of raw product delivered to the oil-contaminated container, and to reduce the number of times the storage container (310) must be replaced during a single treatment and protection process, it is desirable to use a pre-mixed K2CO3 treatment solution having a concentration as high as feasible, taking into account environmental and / or process considerations such as ambient air temperature or the degree or type of oil contamination within the container (330).

[0064] In some cases, step 520 may be performed before step 510. In some cases, step 510 and step 520 are performed simultaneously. After step 520 is completed, the method (500) may proceed to step 530.

[0065] In step 530, a controlled amount of pre-mixed K2CO3 treatment solution is transferred from the storage container (310) to the eductor (380) through conduits (315, 325) and an injection flow control valve (350). Also in step 530, a controlled amount of water, monitored by a flow meter (370), is transferred from the water source (320) to the eductor (380) through conduits (335, 345) and an injection flow control valve (360). The pre-mixed K2CO3 treatment solution and water are mixed in the eductor (380) to form a diluted K2CO3 treatment solution, which is discharged from the eductor (380) through conduits (365). The pre-mixed K2CO3 treatment solution and water must be delivered to the eductor (380) in relative amounts such that the resulting diluted K2CO3 treatment solution contains about 0.1 to about 10 w / w% K2CO3, preferably about 0.25 to about 8 w / w% K2CO3, more preferably about 0.5 to about 7 w / w% K2CO3, even more preferably about 0.75 to about 6 w / w% K2CO3, and even more preferably about 1 to about 5 w / w% K2CO3. In some cases, a diluted K2CO3 treatment solution containing about 1 to about 2 w / w% K2CO3 is formed. After step 530 is completed, the method (500) may proceed to step 540.

[0066] In step 540, the diluted K2CO3 treatment solution is injected into the stainless steel container (330) through the fluid inlet of the container (330) to which the conduit (365) is connected. The diluted K2CO3 treatment solution is injected into the stainless steel container (330) until the container (330) is filled or substantially filled with the diluted K2CO3 treatment solution. The container (330) is filled or substantially filled under an inert atmosphere to minimize oxygen contamination. After step 540 is completed, the method (500) may proceed to step 550.

[0067] In step 550, the diluted K2CO3 treatment solution is maintained in a stainless steel container (330) for a certain period of time to allow petroleum contaminants to penetrate into the treatment solution. In some cases, this "soak" step is performed at room temperature. In some cases, this soak step is performed at a high temperature of up to about 50°C. Generally, the certain period is at least 2 hours. During step 550, the pH of the contents of the stainless steel container is measured. pH measurements can be performed continuously or incrementally over time. Optionally, other chemical analyses, such as petroleum contaminant and / or chloride content, can also be performed during step 550. After step 550 is completed, the method (500) can proceed to step 560.

[0068] In step 560, the used diluted K2CO3 treatment solution is discharged from the container (330) through the fluid outlet and disposed of in the waste container (340), and after this is completed, the K2CO3 A residual film must remain on the inner surface of the vessel (330) during a downtime period to ensure continuous protection from stress corrosion cracking. After step 560 is completed, the method (500) can proceed to step 570.

[0069] In step 570, steps 510 through 560 may be repeated one or more times until it is confirmed that the container (330) no longer contains petroleum contaminants, depending on the pH and optional chemical analysis performed in step 550. At the end of step 570, the method (500) is terminated.

[0070] In some cases, one or more corrosion inhibitors described in this specification may be added in any one of steps 530 to 550.

[0071] Methods according to various embodiments of the present disclosure exhibit many advantages over prior art processes for protecting austenitic stainless steel or austenitic alloy refining equipment from polythionic acid stress corrosion cracking during shutdown operations. First, because the use of soda ash requires adding and mixing water on-site, workers must wear personal protective equipment and avoid dust formation and inhalation. Soda ash dust is also known to irritate the eyes. The use of a pre-mixed K2CO3 solution according to the present invention eliminates the problems associated with the use of soda ash powder. Furthermore, when preparing a soda ash solution on-site, workers must expend considerable time and effort to accurately add a sufficient amount of soda ash to a water tank to prepare a 1- to 5 wt% soda ash solution with a pH of 9 or higher. When using a pre-mixed K2CO3 solution and system according to the present disclosure, such as system (200) and system (300), in-line mixing of water and the pre-mixed K2CO3 solution facilitates the easy preparation of the diluted pre-mixed K2CO3 solution before placement in a stainless steel container. Additionally, when processing a stainless steel container using a soda ash solution in a closed-loop circulation process, the operator must periodically measure the pH of the soda ash solution coming out of the stainless steel container to ensure that the pH is greater than 9, and if the pH is not greater than 9, new soda ash must be added to the solution before recirculating it to the container. On the other hand, when using a pre-mixed K2CO3 solution and system according to the present disclosure, such as system (200) and system (300), the pH of the K2CO3 solution is easily measured in the container to determine whether additional immersion round(s) with the new diluted K2CO3 solution are required.

[0072] Although the present invention and its purposes, features, and advantages have been described in detail, other embodiments are also incorporated into the present invention. All references cited herein are incorporated herein by reference in their entirety. Finally, a person skilled in the art should recognize that the disclosed concepts and specific embodiments can be readily used as a basis for designing or modifying other structures to achieve the same purpose of the present invention without departing from the scope of the present invention as defined in the following claims.

Claims

Claim 1 A system for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking, wherein the system comprises: a storage container configured to store a pre-mixed K2CO3 treatment solution and fluidly coupled to a first conduit; a water source fluidly coupled to a second conduit; a third conduit fluidly coupled to each of the first conduit and the second conduit and fluidly coupled to a stainless steel vessel to be treated; and a waste container fluidly coupled to a stainless steel vessel to be treated. A system comprising, wherein the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of 200g to 1120g of K2CO3 per liter of water, and when the system is used with a stainless steel container, the pre-mixed K2CO3 treatment solution is transferred from the storage container to the third container through the first conduit, and water is transferred from the water source to the third conduit through the second conduit, and the pre-mixed K2CO3 treatment solution and the water are mixed in the third conduit to form a diluted K2CO3 treatment solution containing 0.1 to 10 w / w% K2CO3, and the diluted K2CO3 treatment solution is transferred to the stainless steel container through the third conduit. Claim 2 In claim 1, the system further comprises an injection pump in the first conduit. Claim 3 In claim 1, the system further comprises an injection flow control valve in the first conduit. Claim 4 In claim 1, the system further comprises a water injection flow control valve in the second conduit. Claim 5 In claim 1, the system further comprises a flow meter in the second conduit. Claim 6 In claim 1, the system wherein the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of 800g to 1040g per liter of water. Claim 7 In claim 1, the system wherein the diluted K2CO3 treatment solution contains 1 to 5 w / w% K2CO3. Claim 8 A system for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking, the system comprising: a storage container configured to store a pre-mixed K2CO3 treatment solution and fluidly coupled to a first conduit; a water source fluidly coupled to a second conduit; an eductor coupled to each of the first conduit and the second conduit; a third conduit coupled to the stainless steel vessel to be treated and fluidly coupled to the eductor; and a waste container fluidly coupled to the stainless steel vessel to be treated. A system comprising, wherein the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of 200g to 1120g per liter of water, and when the system is used with a stainless steel container, the pre-mixed K2CO3 treatment solution is transferred from the storage container to the eductor through the first conduit, and water is transferred from the water source to the eductor through the second conduit, and the pre-mixed K2CO3 treatment solution and the water are mixed in the eductor to form a diluted K2CO3 treatment solution containing 0.1 to 10 w / w% K2CO3, and the diluted K2CO3 treatment solution is transferred from the eductor to the stainless steel container through the third conduit. Claim 9 In claim 8, the system further comprises an injection flow control valve in the first conduit. Claim 10 In claim 8, the system further comprises a water injection flow control valve in the second conduit. Claim 11 In claim 8, the system further comprises a flow meter in the second conduit. Claim 12 A system according to any one of claims 8 to 11, wherein the pre-mixed K2CO3 treatment solution has a K2CO3 concentration of 800g to 1040g per liter of water. Claim 13 A system according to any one of claims 8 to 11, wherein the diluted K2CO3 treatment solution contains 1 to 5 w / w% K2CO3. Claim 14 A method for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking, the method comprising: a) incorporating the stainless steel vessel into a system according to any one of claims 1 to 5; b) injecting a diluted K2CO3 treatment solution into the stainless steel vessel until the stainless steel vessel is filled with or substantially filled with the diluted K2CO3 treatment solution; c) maintaining the diluted K2CO3 treatment solution in the stainless steel vessel for a certain period of time; and d) removing the diluted K2CO3 treatment solution from the stainless steel vessel; the method. Claim 15 In paragraph 14, the method wherein the diluted K2CO3 treatment solution is removed from the stainless steel container to the waste container. Claim 16 In claim 14, the above step c) is performed at a maximum temperature of 50°C and the above fixed period is at least 2 hours; or the above step c) is performed at a maximum temperature of 50°C or the above fixed period is at least 2 hours, a method. Claim 17 In paragraph 14, the above step b) is performed in an inert atmosphere. Claim 18 In claim 14, the above step c) further comprises the step of measuring the pH of the contents within the stainless steel container, wherein the contents include the diluted K2CO3 treatment solution. Claim 19 A method for treating a stainless steel vessel to prevent polythionic acid stress corrosion cracking, the method comprising: a) incorporating the stainless steel vessel into a system according to any one of claims 8 to 11; b) injecting the diluted K2CO3 treatment solution into the stainless steel vessel until the stainless steel vessel is filled with or substantially filled with the diluted K2CO3 treatment solution; c) maintaining the diluted K2CO3 treatment solution in the stainless steel vessel for a certain period of time; and d) removing the diluted K2CO3 treatment solution from the stainless steel vessel. Claim 20 In paragraph 19, the method wherein the diluted K2CO3 treatment solution is removed from the stainless steel container to the waste container. Claim 21 In claim 19, the above step c) is performed at a maximum temperature of 50°C and the above fixed period is at least 2 hours; or the above step c) is performed at a maximum temperature of 50°C or the above fixed period is at least 2 hours, a method. Claim 22 In paragraph 19, the above step b) is performed in an inert atmosphere. Claim 23 In claim 19, the above step c) further comprises the step of measuring the pH of the contents within the stainless steel container, wherein the contents include the diluted K2CO3 treatment solution. Claim 24 A system according to any one of claims 1 to 5, wherein the pre-mixed K2CO3 treatment solution further comprises a corrosion inhibitor. Claim 25 A system according to any one of claims 8 to 11, wherein the pre-mixed K2CO3 treatment solution further comprises a corrosion inhibitor. Claim 26 delete Claim 27 delete Claim 28 delete Claim 29 delete Claim 30 delete Claim 31 delete Claim 32 delete Claim 33 delete Claim 34 delete Claim 35 delete Claim 36 delete Claim 37 delete Claim 38 delete Claim 39 delete Claim 40 delete Claim 41 delete Claim 42 delete Claim 43 delete Claim 44 delete Claim 45 delete Claim 46 delete Claim 47 delete Claim 48 delete Claim 49 delete Claim 50 delete Claim 51 delete Claim 52 delete Claim 53 delete Claim 54 delete Claim 55 delete Claim 56 delete Claim 57 delete Claim 58 delete Claim 59 delete Claim 60 delete Claim 61 delete Claim 62 delete Claim 63 delete Claim 64 delete Claim 65 delete Claim 66 delete Claim 67 delete Claim 68 delete Claim 69 delete Claim 70 delete Claim 71 delete Claim 72 delete

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