Method for evaluating the corrosion of a volatile corrosion inhibitor (VCI)
The sealed box test method addresses the issue of moisture penetration in VCI performance evaluation by simulating real-world conditions, enabling accurate assessment of VCI effectiveness through controlled exposure to corrosion agents.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2021-04-01
- Publication Date
- 2026-06-26
AI Technical Summary
Existing corrosion tests for volatile corrosion inhibitors (VCIs), particularly those in paper form, fail to accurately evaluate their performance due to moisture penetration and condensation issues, leading to inaccurate protection against atmospheric corrosion.
A method involving a sealed box test where a VCI and a metallic specimen are conditioned at room temperature, followed by introduction of a corrosion agent, allowing VCI molecules to form a protective layer, and comparing the corrosion of the specimen with a control box without VCI, under controlled temperature conditions to simulate real-world conditions.
This method effectively evaluates the performance of VCIs by ensuring the formation of a protective layer on the metal specimen, providing a more realistic assessment of corrosion resistance and protection against atmospheric corrosion.
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Abstract
Description
Title of the invention: Method for evaluating the corrosion of a volatile corrosion inhibitor (VCI) TECHNICAL FIELD OF THE INVENTION
[0001] The technical field of the invention is that of corrosion tests of a volatile corrosion inhibitor VCI.
[0002] The present invention relates to a method for evaluating the corrosion of a volatile corrosion inhibitor VCI and in particular a method for evaluating the corrosion of a volatile corrosion inhibitor VCI which can be in paper form. TECHNOLOGICAL BACKGROUND OF THE INVENTION
[0003] Volatile corrosion inhibitors, referred to hereafter as VCIs (for example, a film, a paper), exist for the long-term protection of metal surfaces. Specifically, VCIs slow the rate of metal attack and prevent metal corrosion. These chemical solutions, applied directly to the product to be protected, create an invisible barrier, keeping moisture out.
[0004] Some corrosion inhibitors have a paper backing that is not moisture-proof. They are found in paper form for packaging non-cutting parts; they are less expensive to produce than plastic films, which have increased mechanical strength and are water-resistant.
[0005] Corrosion or rust represents a considerable loss of time and money that can quickly become exponential for businesses. VCIs delay and slow the development of corrosion and rust. VCI molecules attach to metal surfaces to form a thin, invisible film only a few molecules thick, thereby reducing the rate of degradation and preventing metal corrosion.
[0006] However, it is necessary to know the performance of a VCI.
[0007] For this purpose, various types of corrosion tests exist, for example, salt spray tests or a vapor inhibition capacity test called the VIA test, which is a laboratory test measuring the outgassing rate of corrosion inhibitor molecules upon contact with a ferrous material. One method is to compare different VIA tests of different VCI materials for the temporary corrosion protection of ferrous metal surfaces.
[0008] The VIA test is performed by bringing the VCI shield into contact with the metal sample and inserting it into a hermetically sealed vial containing water and glycerin. The protected metal sample is located at the top of the vial. The vial is cooled so that the moisture condenses on the protected metal sample. The test measures the time required to achieve a specific corrosion grade, and from these measurements, a VCI molecule deployment rate is calculated. The VIA test provides information on the VCI molecule deployment rate.
[0009] The samples are then inspected to give a value to the corrosion by water visible by a visual examination of the surface of the sample under a microscope.
[0010] The VIA test therefore measures the outgassing rate of corrosion inhibitor molecules and their contact with a material, but not the performance of the VCI. Furthermore, when the performance of paper corrosion inhibitors is tested, moisture penetrates the paper, which disintegrates due to condensation of moisture on the sample, the VCI, and the walls of the flask, and no longer provides protection against atmospheric corrosion.
[0011] There is therefore a need for a test for paper corrosion inhibitors. Summary of the invention
[0012] The invention offers a solution to the problems mentioned above, by allowing a test to be carried out on the one hand with a paper VCI and on the other hand to evaluate their performance and effectiveness.
[0013] A method for evaluating the corrosion of a volatile corrosion inhibitor (also called VCI), the method comprising: • a first step of inserting a volatile corrosion inhibitor and a first corrodible metallic specimen into a first VCI test box comprising an airtight volume when the box is closed, and closing the first airtight box, • a second waiting period for filing protection according to an initial predetermined timeframe, • a third step of inserting a pathogenic corrosion agent such as salt water into a container within the volume of the first sealed box, and sealing the first sealed box, • a fourth stage of waiting for vaporization to prevent corrosion, according to a second stage, • a fifth step of comparing the corrosion of the first metal test specimen with a metal test specimen from a control box.
[0014] Thanks to the invention, this new test makes it possible to evaluate the performance of a volatile corrosion inhibitor (VCI) by allowing the VCI time to transfer molecules onto the metal specimen during the first and second stages, also called the protective conditioning phase, by impregnation of the VCI molecules onto the metal. This protective conditioning phase makes it possible to protect the metal specimen in a manner similar to a For example, a metal part can be packaged in this volatile corrosion inhibitor (VCI). This test is therefore closer to reality than prior art. Furthermore, adding the active corrosion-causing agent to the container in the same environment in which the VCI molecules migrated to form a layer on the metal specimen ensures that the corrosion phase is identical to the protection phase, resulting in a test that more closely resembles reality than prior art methods where the corrosive agent is placed in an environment pre-saturated with VCI molecules. This test is therefore applicable to all types of VCIs, and particularly to solid VCIs such as paper, patches, and plastics.
[0015] In addition to the characteristics mentioned in the preceding paragraph, the method according to one aspect of the invention may have one or more additional characteristics from among the following, considered individually or in all technically possible combinations: • According to one embodiment, the first and second steps are carried out at room temperature and the third and / or fourth step is carried out at a temperature above room temperature. • According to one embodiment, the sealed box is airtight. This provides better insulation between the inside of the box and the ambient air. • In one embodiment, the active agent that inhibits corrosion is liquid. This allows it to vaporize in the box, thus creating a sufficiently humid atmosphere without condensation. • According to one example of this embodiment, the active corrosion-causing agent is introduced at a temperature higher than ambient temperature. This allows it to evaporate without condensing. • As an example, the active pathogenic corrosion agent is a mixture of water and sodium chloride, such as salt water. • According to one embodiment, the ratio of the surface area of the volatile corrosion inhibitor VCI to the volume of the box is greater than or equal to the ratio recommended in a technical data sheet for the volatile corrosion inhibitor VCI. • In one embodiment, the volatile corrosion inhibitor (VCI) is a paper. For example, it comprises a paper support infused with a corrosion-inhibiting active agent that vaporizes and deposits on the metal parts. Indeed, such a test is easily performed with a VCI volatile corrosion inhibitor paper, unlike prior art in which the paper became wet upon contact with the liquid of the corrosion-inhibiting active agent. This new test allows the paper to remain intact. and dry in order to allow the material to be protected against oxidation and corrosion during the process steps. According to one embodiment the first container is removable, for example a plastic container. According to a variant of the previous embodiment, the first box includes walls forming the first container. According to one embodiment, the corrodible metallic test specimen is an iron plate. According to one embodiment, the corrodible metallic test specimen comprises a flat inspection surface and wherein in the first step the metallic test specimen is installed so as to have the flat inspection surface in the open air of the volume of the first VCI test box. According to an example in which, in the first step, the witness is installed so that the flat inspection surface is inclined relative to the bottom of the box. According to one embodiment, the corrodible metallic test specimen is kept away from the volatile corrosion inhibitor VCI and the container. According to one embodiment, in which in the third step the container is positioned such that the volatile corrosion inhibitor VCI is positioned between the metallic test specimen and the active agent pathogenic corrosion. According to one embodiment, in the third step the container is positioned away from the volatile corrosion inhibitor VCI. This prevents the volatile corrosion inhibitor VCI from coming into contact with or absorbing the active corrosion pathogen in the container. According to one embodiment, the first step includes a first substep of positioning the volatile corrosion inhibitor and the first corrodible metallic test specimen and a second substep of closing with a lid on a body of the box after the first substep of insertion. According to an example of this embodiment, the third step includes a first substep of opening the box by removing the cover from the body, and a substep of disposing of the active agent pathogenic corrosion. According to one embodiment, the third step further comprises the insertion of a second corrodible metallic specimen into a second control box comprising an airtight volume when the box is closed, of a pathogenic corrosion agent such as salt water in a second container within the volume of the second airtight box, and of closing the second sealed box, and in that the fifth step includes a rating of the corrosion of the first metal specimen based on the corrosion status of the second metal specimen in the control box. • According to an example of this embodiment, the first VCI test box and the second control box are identical but not their contents in that the second control box does not contain VCI volatile corrosion inhibitor. • According to an example of this embodiment, the first metal test specimen and the second metal test specimen before insertion into one of the boxes are identical. • According to an example of this embodiment, the first active corrosion pathogen and the second active corrosion pathogen are identical. • According to an example of this embodiment, the second container is removable. • According to a variation of the previous example, the second box includes walls forming the second container.
[0016] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures. BRIEF DESCRIPTION OF THE FIGURES
[0017] The figures are presented for illustrative purposes only and are in no way limiting of the invention.
[0018] [Fig. 1] schematically represents the steps of the corrosion evaluation process of a volatile corrosion inhibitor VCI
[0019] [Fig.2] shows a schematic representation of a first VCI test box during a second step of a corrosion evaluation process of a volatile corrosion inhibitor VCI.
[0020] [Fig.3] shows a schematic representation of a first VCI test box during a fourth step of the process.
[0021] [Fig.4] shows a schematic representation of a second control box during a fourth step of the process. DETAILED DESCRIPTION
[0022] The figures are presented for illustrative purposes only and are in no way limiting of the invention.
[0023] Fig. 1 represents a corrosion evaluation method of a volatile corrosion inhibitor 1, also called VCI, according to an embodiment of the invention.
[0024] The corrosion evaluation method for a volatile corrosion inhibitor (VCI) comprises a first step 1E1 of a volatile corrosion inhibitor 1 and a first corrodible metallic specimen 2 into a first VCI test box 3 comprising an airtight volume 30 when box 3 is closed and the closure of the first airtight box. Figure 2 shows the closed box 3 containing the volatile corrosion inhibitor 1 and the first corrodible metallic specimen 2. The VCI test box 3 therefore comprises a body 31 defining the volume 30 and a lid 32 for closing the VCI test box 3 and sealing its volume 30.
[0025] The first step El therefore includes a first sub-step of positioning E10 of the volatile corrosion inhibitor 1 and the first corrodible metallic test specimen 2 and a second sub-step of closing El 1 with the cover 32 on the body 31 of the VCI test box 3 after the first sub-step of insertion E10.
[0026] In this example, the first corrodible metallic test specimen 2 is an iron metal plate comprising a flat inspection surface 20 positioned at an angle to the bottom of the VCI test box 3, and the volatile corrosion inhibitor 1 is a paper. The volatile corrosion inhibitor 1 can be attached to a wall of the VCI test box 3, for example, by taping or gluing it to the lid 32.
[0027] In this embodiment, the first step El is carried out at room temperature.
[0028] In this embodiment, the surface area of the volatile corrosion inhibitor 1 is chosen so that the ratio of the surface area of the volatile corrosion inhibitor 1 to the volume 30 of the inside of the VCI test box 3 is greater than or equal to the ratio recommended in the technical data sheet of the volatile corrosion inhibitor 1.
[0029] The process further comprises a second waiting step for the protective coating E2 to be applied for a predetermined period, for example between two and twenty-four hours. During this waiting step for the protective coating E2, molecules 10 of the volatile corrosion inhibitor evaporate from its support, here the paper, and disperse throughout the volume, some of which are deposited on the flat inspection surface 20 of the metal test specimen 2.
[0030] These molecules 10 are represented roughly on [Fig.2] but of course are actually invisible to the naked eye.
[0031] The process further includes a third step of inserting E3 a corrosion pathogenic active agent 4 such as salt water into a container 43 in the volume 30 of the first sealed box 3, and closing the first sealed box 3.
[0032] Fig. 3 represents the first box 3 comprising the container 43 containing the active corrosion pathogen 4 located in the volume 30 of the box 3 in the closed state.
[0033] The third insertion step E3 therefore includes a first substep E30 of opening the box 3 by removing the cover 32 from the body 31, and a substep of disposing E31 of the active corrosion pathogen 4 which in this example is in a liquid state comprising water and sodium chloride for example salt water.
[0034] In this example of this embodiment, the container 43 is removable and is therefore disposed in this sub-step of disposition E31 on the bottom of the body 31 in the volume 30 with the active corrosion pathogen 4. Of course the active corrosion pathogen 4 could be poured into the container 41 once the latter is disposed on the bottom of the box.
[0035] According to another example not shown, the box 3 includes walls forming the container 43.
[0036] In this embodiment, the process further comprises in this third step E3, a substep E31' of depositing a second corrodible metallic test specimen 2' in a second test box 3' comprising an airtight volume when the test box 3' is closed and of a pathogenic corrosion active agent 4' such as salt water in a second container 43' in the volume of the second test box 3' and of closing the second test box 3'.
[0037] Figure 4 represents this second sealed control box 3'. The second sealed control box 3' is therefore devoid of volatile corrosion inhibitor 1. This second control box 3' allows the effectiveness of the volatile corrosion inhibitor 1 to be compared with the first box 3.
[0038] The third step E3 therefore includes in this embodiment, a substep of closing E32 the two boxes 3, 3' with their respective lid 32, 32' on their respective body 31, 31' after the first substep of deposition E31, E31'.
[0039] The first test box VCI 3 is identical to the second control box 3', but not in its contents, since the second lacks the volatile corrosion inhibitor. The first and second volumes of the active corrosion pathogen are identical and come from the same mixture in a container. The second volume of the active corrosion pathogen 4' is therefore, in this example, salt water.
[0040] According to one example of this embodiment, the pathogens 4, 4' are placed in the test box VCI 3 and in the control box 3' at a temperature higher than the ambient temperature, i.e., the temperature of the volume of box 3 when the first and second steps were carried out. This allows, upon closing each box, for some of the active corrosion agent to evaporate.
[0041] The process finally includes a fourth step of waiting for vaporization of corrosion E4 for a second period of time. This second period can be predetermined, for example 3 days, or can be based on a corrosion condition of the metal specimen 2' visible from the outside through a transparent wall of the control box 3'. For example, if the control box (3') and the VCI test box (3) do not show corrosion of the specimens (equal results), the test continues until a situation is reached where the second metal specimen is corroded.
[0042] During this time period, molecules 40 of the active corrosion pathogen 4, here water and salt molecules, are deposited on the first metal test specimen coated with a layer of molecules 10 of the volatile corrosion inhibitor, and molecules 40' of the active corrosion pathogen 4 are deposited on the second metal test specimen 2' of the control plate 3', which will corrode. The molecules 40 of the active corrosion pathogen 4 deposited on the layer of molecules 10 of the flat inspection surface 20 of the metal test specimen 2 will be inactive depending on the performance of the active corrosion pathogen 4, which more or less effectively prevents corrosion of the metal test specimen 2.
[0043] In this example of this embodiment, the fourth step is carried out by placing the two boxes in an oven or heating device 5, which raises the temperature of the active corrosion pathogen above ambient temperature to increase its vaporization in the sealed boxes. For example, the oven is at 60°C, increasing the vaporization rate of each active corrosion pathogen 4 and 4'.
[0044] The process finally includes a fifth step of comparison E5 of the corrosion of the first metal specimen and in this embodiment a notation based on the difference between the corroded state of the first metal specimen 2 and the corrosion state of the second metal specimen 2'.
[0045] This process makes it possible to demonstrate the effectiveness of a volatile corrosion inhibitor, here VCI paper, intended to protect against atmospheric corrosion, if the flat inspection surface 20 of the first metal test specimen 2 is not corroded while that of the control box 3' is corroded.
[0046] Unless otherwise specified, the same element appearing on different figures presents a unique reference.
Claims
Demands
1. A method for evaluating the corrosion of a volatile corrosion inhibitor (VCI), the method comprising: - a first step of inserting (E1) a volatile corrosion inhibitor (1) and a first corrodible metallic specimen (2) into a first VCI test box (3) comprising an airtight volume when the box is closed, and closing the first airtight box (3), - a second step of waiting for protective deposition (E2) for a first predetermined time, - a third step of inserting (E3) a corrosion pathogenic active agent (4) such as salt water in a container into the volume of the first airtight box (3), and closing the first airtight box (3), - a fourth step of waiting for vaporization for corrosion (E4) for a second predetermined time,- a fifth comparison step (E5) of the corrosion of the first metallic specimen (2) with a metallic specimen from a control box.
2. Method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to the preceding claim wherein, the volatile corrosion inhibitor (1) is in paper form.
3. A method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to any one of the preceding claims, wherein the first step (E1) and second step (E2) are carried out at room temperature and wherein the third (E3) and / or fourth step (E4) are carried out at a temperature above room temperature.
4. A method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to any one of the preceding claims, wherein the active agent pathogenic to corrosion is liquid.
5. A method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to any one of the preceding claims, wherein the ratio of the surface area of the volatile corrosion inhibitor (1) to the volume (30) of the container (3) is greater than or equal to the ratio recommended in a technical data sheet for the volatile corrosion inhibitor (1).
6. A method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to any one of the preceding claims, wherein the first corrodable metallic specimen (2) comprises a flat inspection surface (20) and wherein in the first step (11) the metallic specimen (2) is installed so as to have the flat inspection surface (20) in the open air of the volume (30) of the first VCI test box (3).
7. Method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to any one of the preceding claims, wherein the first step (El) comprises a first substep of positioning (E10) the volatile corrosion inhibitor (1) and the first corrodible metallic specimen (2) and a second substep of closing (Eli) with a cover (32) on a body (31) of the box (3) after the first substep of insertion (E10).
8. A method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to the preceding claim, wherein the third step (E3) comprises a first substep (E30) of opening the box (3) by removing the cover (32) from the body (31), and a substep of disposing (E31) of the active corrosion pathogenic agent (4).
9. A method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to any one of the preceding claims, wherein the third step (E3) further comprises inserting a second corrodable metallic specimen (2') into a second control box (3') comprising an airtight volume when the control box (3') is closed, a corrosion pathogen (1') such as salt water into a second container (43') in the volume of the second airtight control box (3') and closing the second airtight control box (3'), and wherein the rating in the fifth (E5) is based on the difference between the corroded state of the first metallic specimen (2) and the corrosion state of the second metallic specimen (2').
10. A method for evaluating the corrosion of a volatile corrosion inhibitor (1) according to claim 9, wherein the first VCI test box (3) and the second control box (3') are identical, the first metal specimen (2) and the second metal specimen (2') are identical and the first active corrosion pathogen (1) and the second active corrosion pathogen (1') are identical.