FORMULATION OF CORROSION INHIBITORS FOR GEOTHERMAL REINJECTION WELLS

Abstract

A method is provided for inhibiting corrosion of a metal surface in contact with a geothermal system. The method may include contacting the metal surface with a corrosion-inhibiting composition by adding the composition to the geothermal process water. The corrosion-inhibiting composition may include an organic phosphonate, an orthophosphate, and zinc or a zinc salt.

Description

FORMULATION OF CORROSION INHIBITORS FOR GEOTHERMAL REINJECTION WELLS BACKGROUND 1. Field of the invention The present invention generally relates to corrosion inhibition. More particularly, this disclosure relates to a composition for inhibiting corrosion in a geothermal system. 2. Description of the related technique Geothermal energy is energy in the form of heat within the Earth's interior, which can be harnessed using geothermal wells. The Earth's interior contains a vast reservoir of heat, but challenges remain in extracting this heat to generate power. Geothermal energy moves to the Earth's surface through thermal conduction in solid rock. Thermal energy can also be transmitted to the surface by the movement of molten rock or by the circulation of fluid (H₂O in the form of steam or water) through interconnected fractures and pores. Geothermal wells are, in any case, relatively deep wells. Geothermal brines and steam are commonly used as energy sources. Geothermal brine is used for power generation, heating, and electrical processes. Geothermal steam temperatures range from approximately 185°C to approximately 370°C (approximately 365°F to approximately 700°F). Steam is separated from the brine using flash evaporation units. Low-temperature brines can also be used to produce binary units of electricity (secondary fluid units). Geothermal brines can have a salinity ranging from less than approximately 1,000 ppm to several hundred thousand ppm and a non-condensable gas content of up to approximately 6 percent. Depending on the salt content and application, geothermal fluids can be used directly or through a secondary fluid cycle.The use of geothermal energy as a power source has increased in importance as other energy sources become less abundant and more expensive. It is a sustainable, renewable energy source, and unlike some other renewable sources, geothermal energy is constantly available. Corrosion of metal surfaces in aqueous environments is a problem in the geothermal industry. For example, geothermal operations involve contacting metal surfaces with corrosive components such as brines. These aggressive components can cause severe corrosion, as evidenced by surface pitting, brittleness, and overall metal loss. The metal surfaces may be composed of high-alloy steels, including chromium steels, ferritic alloy steels, austenitic stainless steels, precipitation-hardened stainless steels, and high-nickel steels. OI o» BRIEF COMPENDIUM A method is provided for inhibiting corrosion of a metal surface in contact with a geothermal system. The method may include contacting the metal surface with a corrosion-inhibiting composition. The corrosion-inhibiting composition may comprise an organic phosphonate, an orthophosphate, and zinc or a zinc salt. In some respects, organic phosphonate can be 2,2'-(hydroxyphosphoryl)disuccinic acid (PSO), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), ((dimethylamino)methylene)bis(phosphonic acid) (DMAMDP), N,N-dimethyl-1,1-diphosphonomethanamine oxide (DMAMDPO), (morpholinomethylene)bis(phosphonic acid) (MMDP), 4-(diphosphonomethyl)morpholine oxide (MMDPO), hydroxyphosphonoacetic acid (HPA), phosphinocarboxylic acids (PCA), or any combination thereof. In some respects, the corrosion-inhibiting composition can range from approximately 1% by weight to approximately 20% by weight of the organic phosphonate. In some respects, the corrosion-inhibiting composition can range from approximately 10% by weight to approximately 40% by weight of orthophosphate. In some respects, the corrosion-inhibiting composition can range from approximately 2% by weight to approximately 15% by weight of zinc or zinc salt. In some aspects, the corrosion-inhibiting composition may also include a fluorescent tracer. In some aspects, the corrosion-inhibiting composition may comprise from approximately 0.01% by weight to approximately 0.5% by weight of the fluorescent tracer. In some aspects, the method may include passivating the metal surface with the corrosion-inhibiting composition. In some aspects, the metal surface may be in contact with an aqueous medium comprising from approximately 50 ppm to approximately 400 ppm of the corrosion-inhibiting composition. In some aspects, the metal surface may be in contact with an aqueous medium comprising a pH from approximately 4 to approximately 8. In some respects, the corrosion-inhibiting composition can be added to the aqueous medium at a dosage rate from approximately 0.01 ppm to approximately 500 ppm. In some respects, the metallic surface may be iron, copper, an iron alloy, a copper alloy, admiralty brass, approximately 90% copper and approximately 10% nickel, approximately 80% copper and approximately 20% nickel, approximately 70% copper and approximately 30% nickel, aluminum brass, manganese brass, leaded naval bronze, phosphor bronze, carbon, and any combination thereof. In some aspects, the metallic surface may comprise iron. In some aspects, the surface of the metal may be mild steel or carbon steel. In some aspects, the corrosion rate of the metal surface may be less than approximately 3 mpy. ινΐΛ / a / zuz i / un oio» In some respects, the corrosion rate of the metal surface may be less than approximately 1 mpy. In some respects, the corrosion-inhibiting composition may comprise a water-miscible cosolvent. In some respects, the water-miscible cosolvent can be selected from the group consisting of: acetone, methanol, ethanol, propanol, formic acid, formamide, propylene glycol, ethylene glycol, and any combination thereof. In some aspects, the corrosion-inhibiting composition may comprise an additive selected from the group consisting of: an additional corrosion inhibitor, a treatment polymer, an antimicrobial agent, an antiscalant, a colorant, a filler, a buffer, a surfactant, a viscosity modifier, a chelating agent, a dispersant, a deodorant, a masking agent, an oxygen scavenger, an indicator dye, and any combination thereof. The use of a corrosion-inhibiting composition to inhibit corrosion of a metallic surface in contact with an aqueous medium in a geothermal system is also provided. The corrosion-inhibiting composition may include an organic phosphonate, an orthophosphate, and zinc or a zinc salt. The foregoing has provided a fairly comprehensive summary of the technical features and advantages of the present disclosure, so that the detailed description that follows may be better understood. Further features and advantages of the disclosure, which form part of the subject matter of the claims of this application, will be described later herein. Those skilled in the art should appreciate that the specific design and embodiments disclosed herein can readily be used as a basis for modifying or designing other embodiments to accomplish the same purposes as the present disclosure. Those skilled in the art should also realize that such equivalent embodiments do not depart from the spirit and scope of the disclosure as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS A detailed description of the invention follows, with specific reference to the drawings in which: FIG. 1 shows corrosion data for the chemistry and metallurgy of geothermal reinjection well water; and FIG. 2 shows the corrosion rate in mpy over time for various chemistries compared to no treatment. DETAILED DESCRIPTION Several modalities are described below. The relationship and functioning of the various elements of the modalities can be better understood by referring to the following detailed description. However, the modalities are not limited to those illustrated below. In certain cases, details that are not necessary for understanding the modalities described herein may have been omitted. ML / a / ZUZl 01 o» A method is provided for inhibiting corrosion of a metal surface in contact with a geothermal system. The method may include contacting the metal surface with a corrosion-inhibiting composition. The corrosion-inhibiting composition may comprise an organic phosphonate, an orthophosphate, and zinc or a zinc salt. In some respects, organic phosphonate can be 2,2'-(hydroxyphosphoryl)disuccinic acid (PSO), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), ((dimethylamino)methylene)bis(phosphonic acid) (DMAMDP), β-dimethyl-1,1-diphosphonomethanamine oxide (DMAMDPO), (morpholinomethylene)bis(phosphonic acid) (MMDP), 4-(diphosphonomethyl)morpholine oxide (MMDPO), hydroxyphosphonoacetic acid (HPA), phosphinocarboxylic acids (PCA), or any combination thereof. In some respects, organic phosphonate may be PSO. In some respects, organic phosphonate may be PBTC. In some respects, organic phosphonate may be DMAMDP. In some respects, organic phosphonate may be DMAMDPO. In some respects, organic phosphonate may be MMDP. In some respects, organic phosphonate may be MMDPO. In some respects, organic phosphonate may be HPA. In some respects, organic phosphonate may be PCA. The corrosion-inhibiting composition may include an effective amount of organic phosphate to maximize corrosion inhibition. The amount of organic phosphonate in the composition can range from approximately 1% to approximately 20% by weight. Specifically, the amount of organic phosphonate in the corrosion-inhibiting composition may be approximately 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, or 19% by weight. The corrosion-inhibiting composition may include an effective amount of orthophosphate to maximize corrosion inhibition. The composition may contain from approximately 10% to approximately 40% by weight of orthophosphate. In some formulations, the amount of orthophosphate may be approximately 15%, 20%, 25%, 30%, 35%, or 40% by weight. The corrosion-inhibiting composition may comprise an effective amount of zinc or a zinc salt to maximize corrosion inhibition. In some aspects, the corrosion-inhibiting composition may comprise from approximately 2% to approximately 15% by weight of zinc or a zinc salt. In some aspects, the amount of zinc in the composition may be approximately 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15% by weight. In some aspects, the corrosion inhibitor composition may also include a fluorescent tracer. In some aspects, the composition may include an inert tracer, which is made compatible with fluorescent tracing technology such as TRASAR® technology (available from Nalco® Company, Naperville, Illinois, USA). In other aspects, an inert fluorescent tracer may be included in the composition to provide a means of determining the dosage level. A known proportion of the fluorescent tracer may be added either simultaneously or sequentially with the corrosion inhibitor. Effective inert fluorescent tracers may include substances that are chemically non-reactive with other system components and that do not degrade significantly over time. Representative inert fluorescent tracers include fluorescein or fluorescein derivatives; rhodamine or rhodamine derivatives; naphthalenesulfonic acids (mono, di, tri, etc.); pyrenesulfonic acids (mono, di, tri, tetra, etc.); stilbene derivatives containing sulfonic acids (including optical brighteners); biphenylsulfonic acids; phenylalanine; tryptophan; tyrosine; vitamin B2 (riboflavin); vitamin B6 (pyridoxine); vitamin E (α-tocopherols); ethoxyquin; caffeine; vanillin; condensation polymers of formaldehyde and naphthalenesulfonic acid; condensates of formaldehyde and phenylsulfonic acid; lignosulfonic acids; polycyclic aromatic hydrocarbons; (Poly)cyclic aromatic hydrocarbons containing amine, phenol, sulfonic acid, carboxylic acid functionalities in any combination; (Poly)heterocyclic aromatic hydrocarbons having N, O or S;a polymer containing at least one of the following residues: naphthalenesulfonic acids, pyrenesulfonic acids, biphenylsulfonic acids or stilbenesulfonic acids.; In some aspects, the corrosion inhibitor composition can range from approximately 0.01% by weight to approximately 0.5% by weight of the fluorescent tracer. The amount of fluorescent tracer in the composition, or added separately, may be sufficient to track the dosage level of the corrosion inhibitor in the aqueous system. In some respects, the metal surface may be iron, copper, an iron alloy, a copper alloy, admiralty brass, approximately 90% copper and approximately 10% nickel, approximately 80% copper and approximately 20% nickel, approximately 70% copper and approximately 30% nickel, aluminum brass, manganese brass, leaded naval bronze, phosphor bronze, carbon, and any combination thereof. In some respects, the metal surface may comprise iron. In some respects, the metal surface may be mild steel or carbon steel. In some aspects, the method may include passivating the metal surface with the corrosion-inhibiting composition. Passivating the metal surface may involve adding the composition directly to a metal surface or adding the composition to an aqueous system at a higher dosage for a certain period of time and then reducing the dosage to a maintenance dose. In some aspects, the metal surface may be in contact with an aqueous medium comprising from approximately 50 ppm to approximately 400 ppm of the corrosion-inhibiting composition. In some aspects, the corrosion inhibitor can be added to the aqueous medium at a concentration from approximately 1 ppm to approximately 1000 ppm, from approximately 1 ppm to approximately 800 ppm, from approximately 1 ppm to approximately 600 ppm, from approximately 1 ppm to approximately 500 ppm, from approximately 1 ppm to approximately 400 ppm, from approximately 1 ppm to approximately 200 ppm, from approximately 5 ppm to approximately 1000 ppm, from approximately 5 ppm to approximately 800 ppm, from approximately 5 ppm to approximately 600 ppm, from approximately 5 ppm to approximately 500 ppm, from approximately 5 ppm to approximately 400 ppm, or from approximately 5 ppm to approximately 200 ppm. In some aspects, the corrosion inhibitor composition can be added to the aqueous medium at a dosage rate from approximately 0.01 ppm to approximately 500 ppm. In some aspects, the metal surface may be in contact with an aqueous medium that has a pH from approximately 4 to approximately 8. In some aspects, the pH of the aqueous medium is approximately 4.5, approximately 5, approximately 5.5, approximately 6, approximately 6.5, approximately 7, or approximately 7.5 The compositions described herein are capable of reducing the corrosion rate of metal surfaces in contact with an aqueous medium in a geothermal system. The corrosion rate of the metal surface can be reduced to less than approximately 3 mpy. In some cases, the corrosion rate of the metal surface can be reduced to less than approximately 2.5 mpy, approximately 2 mpy, 1.5 mpy, or approximately 1 mpy. In some aspects, the corrosion-inhibiting composition may include a water-miscible cosolvent. Examples of water-miscible cosolvents include, but are not limited to, acetone, methanol, ethanol, propanol, formic acid, formamide, propylene glycol, or ethylene glycol. The corrosion-inhibiting composition may include an additive. Examples of additives include, but are not limited to, an additional corrosion inhibitor, a treatment polymer, an antimicrobial agent, an antiscalant, a colorant, a filler, a buffer, a surfactant, a viscosity modifier, a chelating agent, a dispersant, a deodorant, a masking agent, an oxygen scavenger, an indicator dye, or an antifoaming agent. In some aspects, the method may involve adding an antifoaming agent to the process water used in the geothermal system. The process water may be geothermal cooling water or geothermal condensate. Examples of antifoaming agents include, but are not limited to, C5-C25 alkyl alcohols, C5-C25 alkyl alcohol ethoxylates, monobasic aluminum stearate, stearic acid, polydimethylsiloxane, sorbitan monostearate, hydrated silica, ethoxylated sorbitan monostearate, xanthan gum, and amorphous silica. In some embodiments, the antifoaming agent may consist of water, polydimethylsiloxane, and sorbitan monostearate. In other aspects, the antifoaming agent may consist of water, polydimethylsiloxane, sorbitan monostearate, hydrated silica, ethoxylated sorbitan monostearate, and xanthan gum. In some aspects, the antifoaming agent can be added to the process water in amounts ranging from approximately 0.001 ppm to approximately 100 ppm. In some embodiments, the antifoaming agent can be added to the process water in amounts ranging from approximately 0.001 ppm to approximately 10 ppm, approximately 0.001 ppm to approximately 5 ppm, approximately 0.01 ppm to approximately 10 ppm, approximately 0.05 ppm to approximately 5 ppm, approximately 0.05 ppm to approximately 2 ppm, approximately 0.05 ppm to approximately 10 ppm, or approximately 0.1 ppm to approximately 1 ppm. In some aspects, an iron catalyst may be added to the process water. In other aspects, an iron catalyst is not added to the process water. The iron catalyst may include iron salts, iron complexes, or combinations thereof. Iron catalysts may include, for example, ferrous sulfate, ferric sulfate, ferric chloride, ferrous gluconate, ferric nitrate, iron(III) hydroxide oxide [FeO(OH)], ferrous chloride, ferrous iodide, iron sulfide, ferric 4-cyclohexylbutyrate, ferric oxide, ferric bromide, ferrous fluoride, iron powder, ferrous acetate, ferrous oxalate, ferric oxalate, and similar compounds. In some aspects, hydrogen peroxide may be added to the process water. In other aspects, hydrogen peroxide is not added to the process water. Additional corrosion inhibitors, which may be included in the composition or added separately to the process water, consist of a fatty acid monomer or oligomer, such as saturated and unsaturated CU-C22 fatty acids, as well as dimers, trimers, and oligomer products obtained by polymerizing one or more of these fatty acids. The corrosion inhibitor may be a triazole. Examples of triazoles include, but are not limited to, benzotriazole, tolyltriazole, butylbenzotriazole, halobenzotriazole, halo-tolyltriazole, or nitrated triazoles. In some respects, the additional corrosion inhibitor may be a 2-substituted benzimidazole. In some embodiments, the additional corrosion inhibitor may include benzyl-(C12-C16 alkyl)dimethylammonium chloride. In some embodiments, the corrosion inhibitor comprises benzyl-(C12-C16 alkyl)dimethylammonium chloride, an ethoxylated alcohol phosphate salt, an imidazoline salt, 2-mercaptoethanol, ethylene glycol, diethylene glycol, methanol, 2-butoxyethanol, and water. In some embodiments, the corrosion inhibitor comprises sodium gluconate. EXAMPLES Example 1 The compounds used in these examples include phosphonate (CAS No. 770734-50-4), phosphoric acid (CAS No. 7664-38-2), zinc chloride (CAS No. 7646-85-7), and a fluorescent marker (CAS No. 5957210-0). Composition 1 includes PSO, phosphoric acid, zinc chloride, and a fluorescent marker. Composition 2 includes imidazoline acetates from tall oil, quaternary ammonium compounds, and substituted carboxylic acids. A composition containing molybdate (MoO4) was tested as a corrosion inhibitor under conditions mimicking geothermal reinjection well water. However, high doses of molybdate were required to achieve acceptable corrosion inhibition. Unexpectedly, a composition containing a phosphonate, phosphoric acid, and zinc was found to provide the best corrosion inhibition, even at a pH of approximately 5 to 6.5 in the geothermal reinjection well. Gamry corrosion data were obtained by mimicking the reinjection well conditions at the lowest pH. The measured corrosion rate was less than approximately 1 mpy. Figure 1 shows the corrosion rate for different chemistries. The mean corrosion rate on the blank was 7.35 mpy. Composition 1 outperformed the other chemistries with a corrosion rate of 0.67 mpy (the coupon appeared clear with no corrosion). The metal coupon was passivated using approximately 100 ppm of Composition 1 for 18 hours, and then the dosage was reduced to approximately 15 ppm for 24 hours. The coupon treated with MoO4 had begun to corrode visibly. The mean corrosion rate was 2.1 mpy for 30 ppm of MoCh and 1.32 mpy for 50 ppm of MoO4. The coupons treated with MoO4 were passivated using 100 ppm of MoO4 for 18 hours, and then the dosage was reduced to 30 ppm and 50 ppm of MoO4. Example 2 Water containing 1.3 ppm Ca, 0.1 ppm Mg, 68 ppm alkalinity as CaCO3, and 93 ppm sulfate ion was prepared to simulate geothermal reinjection well water. The pH of the water was adjusted to 6.3 using dilute sulfuric acid. Approximately one liter of water was added to a Gamry cell, and an inhibitor was added for passivation according to Table 1. The corrosion rate was measured for approximately 18 hours. The water was then replaced with fresh water containing the maintenance dosage of inhibitor, and the water was heated to approximately 40°C. The pH was maintained between approximately 6 and 6.3 for approximately 24 hours. TABLE 1 ινΐΛ / a / zuz 1 / un o 1 o» Passivation Inhibitor Test 18 hours at room temperature Maintenance Dose 24 hours at 40 °C pH 1 Comp. 1 100 ppm 15 ppm 6-6.3 2 Comp. 1 100 ppm 25 ppm 6-6.3 3 MoO4 (25%) 100 ppm 30 ppm 6-6.3 4 MoO4 (25%) 100 ppm 50 ppm 6-6.3 5 MoO4 (25%) 100 ppm 100 ppm 6-6.3 6 Comp. 2 100 ppm 30 ppm 6-6.3 The metal was mild steel, and Composition 1 provided the best corrosion control at a dosage of approximately 15 ppm. No corrosion was observed on the coupons treated with Composition 1. The average corrosion rate was approximately 0.6 mpy. Figure 2 shows the corrosion rate for the different tests over time. The average corrosion rate for MoO4 at a dosage of 50 ppm was approximately 1.3 mpy, but the coupon began to corrode, which was comparatively better than at 30 ppm of MoO4. Metal coupons treated with Composition 2 began to corrode during the 100 ppm passivation stage, and the average corrosion rate was 4.0 mpy. The blank corrosion rate was above approximately 5 mpy, even at room temperature. Any composition described herein may comprise, consist of, or essentially consist of any of the compounds / components described herein. For the purposes of this disclosure, the phrases "essentially consist of," "essentially consists of," "essentially consists of," and the like limit the scope of a claim to the specified materials or steps and those materials or steps that do not substantially affect the basic and novel feature(s) of the claimed invention. As used herein, the term “approximately” means the quoted value within the errors arising from the standard deviation found in their respective test measurements, and if those errors cannot be determined, then “approximately” means within 5% of the quoted value. Any method disclosed herein may comprise, consist of, or consist essentially of any step of the method disclosed herein or any combination of two or more of the steps of the method disclosed herein. Unless otherwise specified, all molecular weights referenced herein are weight average molecular weights and all viscosities were measured at 25 °C with pure (undiluted) polymers. All compositions and methods described and claimed herein can be made and implemented without undue experimentation in light of this description. Although this invention can be carried out in many different ways, specific preferred embodiments of the invention are described herein in detail. This description is an example of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. Furthermore, unless expressly stated otherwise, the use of the term "a" is intended to include at least one or one or more. For example, "a dispersant" is intended to include at least one dispersant or one or more dispersants. Any range given in absolute or approximate terms is intended to encompass both, and any definition used herein is for the purpose of clarification and not for limitation.Although the ranges and numerical parameters that define the broad scope of the invention are approximations, the numerical values ​​stated in the specific examples are reported as accurately as possible. However, any numerical value inherently contains certain errors that necessarily result from the standard deviation found in its respective test measurements. Furthermore, it should be understood that all ranges disclosed herein encompass any and all subranges (including all fractional and whole values) included therein. Furthermore, the invention encompasses any and all possible combinations of some or all of the various embodiments described herein. It should also be understood that various changes and modifications to the preferred embodiments described herein will be evident to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the invention and without diminishing its intended advantages. Therefore, it is intended that such changes and modifications be addressed in the appended claims.

Claims

1. A method for inhibiting corrosion of a metallic surface in contact with a geothermal system, comprising: contacting the metallic surface with a corrosion-inhibiting composition, the corrosion-inhibiting composition comprising an organic phosphonate, an orthophosphate and zinc or a salt thereof.

2. The method of claim 1, wherein the organic phosphonate is 2,2'(hydroxyphosphoryl)disuccinic acid (PSO), 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), ((dimethylamine)methylene)bis(phosphonic acid) (DMAMDP), A / ,A / -dimethyl-1,1-diphosphonomethanamine oxide (DMAMDPO), (morpholinomethyl)bis(phosphonic acid) (MMDP), 4-(diphosphonomethyl)morpholine 4-oxide (MMDPO), hydroxyphosphonoacetic acid (HPA), phosphinocarboxylic acids (PCA), or any combination thereof.

3. The method of any one of claims 1-2, wherein the corrosion-inhibiting composition comprises from approximately 1% by weight to approximately 20% by weight of the organic phosphonate.

4. The method of any one of claims 1-3, wherein the corrosion-inhibiting composition comprises from approximately 10% by weight to approximately 40% by weight of orthophosphate.

5. The method of any one of claims 1-4, wherein the corrosion-inhibiting composition comprises from approximately 2% by weight to approximately 15% by weight of zinc or the zinc salt thereof.

6. The method of any one of claims 1-5, wherein the corrosion-inhibiting composition further comprises a fluorescent tracer.

7. The method of claim 6, wherein the corrosion-inhibiting composition comprises from approximately 0.01% by weight to approximately 0.5% by weight of the fluorescent tracer.

8. The method of any one of claims 1-7, further comprising passivating the metal surface with the corrosion-inhibiting composition.

9. The method of any one of claims 1-8, wherein the metal surface is in contact with an aqueous medium comprising from approximately 50 ppm to approximately 400 ppm of the corrosion-inhibiting composition.

10. The method of any one of claims 1-9, wherein the metal surface is in contact with an aqueous medium comprising a pH from approximately 4 to approximately 8.

11. The method of any one of claims 1-10, wherein the corrosion-inhibiting composition is added to the aqueous medium at a dosage rate from approximately 0.01 ppm to approximately 500 ppm.

12. The method of any one of claims 1-11, wherein the metal surface comprises iron, copper, an iron alloy, a copper alloy, admiralty brass, approximately 90% copper and approximately 10% nickel, approximately 80% copper and approximately 20% nickel, approximately 70% copper and approximately 30% nickel, aluminum brass, manganese brass, leaded naval bronze, phosphor bronze, carbon, and any combination thereof.

13. The method of any one of claims 1-12, wherein the metallic surface comprises iron.

14. The method of any one of claims 1-13, wherein the metal surface is mild steel or carbon steel.

15. The method of any one of claims 1-14, wherein the corrosion rate of the metal surface is less than approximately 3 mpy.

16. The method of any one of claims 1-15, wherein the corrosion rate of the metal surface is less than approximately 1 mpy.

17. The method of any one of claims 1-16, wherein the corrosion-inhibiting composition comprises a water-miscible cosolvent.

18. The method of claim 17, wherein the water-miscible cosolvent is selected from the group consisting of: acetone, methanol, ethanol, propanol, formic acid, formamide, propylene glycol, ethylene glycol, and any combination thereof.

19. The method of any of claims 1-18, wherein the corrosion-inhibiting composition comprises an additive selected from the group consisting of: an additional corrosion inhibitor, a treatment polymer, an antimicrobial agent, an antiscalant agent, a colorant, a filler, a buffer, a surfactant, a viscosity modifier, a chelating agent, a dispersant, a deodorant, a masking agent, an oxygen scavenger, an indicator dye, and any combination thereof.

20. Use of a corrosion-inhibiting composition to inhibit corrosion of a metallic surface in contact with an aqueous medium in a geothermal system, wherein the corrosion-inhibiting composition comprises an organic phosphonate, an orthophosphate and zinc or a salt thereof.