USOO644.7717B1 (12) United States Patent (10) Patent No.: US 6,447,717 B1 Fan et al. (45) Date of Patent: Sep. 10, 2002 (54) COMPOSITION AND METHOD FOR 5,284,512 A 2/1994 Koskan et al. .............. 106/416 INHIBITION OF METAL CORROSION 5,443,651 A 8/1995 Kalota et al. .................. 134/2 5,531,934. A 7/1996 Freeman et al. ............ 252/390 (75) Inventors: Joseph C. Fan; Lai-Duien Grace Fan, SE A : 3.E. been al - - - - - - - - - - - - - - 5. -- . 2Y----Y/2 arey el al. WN is Critish Mazo, 5,616,544. A 4/1997 Kalota et al. ............... 508/508 1Imelle, all O 5,776,875 A 7/1998 Tang et al. ................. 510/247 5,853,619 A 12/1998 Watson et al. .............. 252/391 (73) ASSignee: lar Corporation, Bedford Park, IL 6,117,364 A * 9/2000 Vorderbruggen et al. ... 252/395 (*) Notice: Subject to any disclaimer, the term of this * cited bby examiner patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days. Primary Examiner Krisanne Thornton (74) Attorney, Agent, or Firm-Olson & Hierl, Ltd. (21) Appl. No.: 09/325,985 (57) ABSTRACT (22) Filed: Jun. 4, 1999 Carbon dioxide induced corrosion of ferrous metals in (51) Int. Cl." ................................................. C23F 11/00 aqueous Systems is inhibited by treatment of the aqueous (52) U.S. Cl. ................ ... 422/7; 422/12; 422/17 System with corrosion inhibiting amino thiol and amino (58) Field of Search s 4227 12, 17 disulfide compounds. Particularly effective inhibitors are the - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - s u-1-9 natural amino acids cysteine and cystine and their decar (56) References Cited boxylated analogues cysteamine and cyStamine. Novel cor rosion inhibiting compositions comprising a combination of U.S. PATENT DOCUMENTS amino thiol or amino disulfide compounds with acidic amino 4,971,724. A 11/1990 Kalota et al. ............... so acid polymers are also disclosed. 5,116,513 A 5/1992 Koskan et al. .... ... 210/698 5,152.902. A 10/1992 Koskan et al. .............. 210/698 14 Claims, No Drawings US 6,447,717 B1 1 2 COMPOSITION AND METHOD FOR cations are highly toxic and in Some cases non INHIBITION OF METAL CORROSION biodegradable. Many corrosion inhibitors interfere with the oil-water Separation process, which interference results in TECHNICAL FIELD relatively larger amounts of crude oil contaminants in the This invention relates to a composition and method for produced water that is discharged into the ocean after inhibiting the corrosion of metals in carbon dioxide con Separation. taining aqueous Systems. More particularly, this invention There is a growing concern regarding the environmental relates to the use of amino thiol or amino disulfide com impact of Scale and corrosion inhibitors, as well as the oil pounds as corrosion inhibitors in carbon dioxide containing contaminants that are currently being released into Sensitive aqueous Systems. This invention further relates to the use of marine ecosystems. Such as the North Sea through their use acidic amino acid polymers together with the amino thiol or in the oil production industry. disulfide compounds as corrosion inhibitors in carbon diox Polyaspartates are biodegradable, low toxicity materials ide containing aqueous Systems. with known corrosion inhibiting activity. U. S. Pat. No. 5,607,623 to Benton, et al. describes the use of polyaspar BACKGROUND OF THE INVENTION 15 tates to inhibit ferrous metal corrosion in carbon dioxide Oil bearing geologic formations generally contain mix containing aqueous Systems. Polyaspartates are useful cor tures of crude oil and mineral laden waters, hereinafter rosion inhibitors, affording 70 to 85% corrosion inhibition in referred to as formation waters. Oil wells produce a mixture carbon dioxide containing oilfield brines. In addition, U.S. of crude oil and formation water. AS wells age, the natural Pat. Nos. 5,116,513 and 5,152,902 to Koskan et al. disclose preSSures within the formation decrease, thus leading to the use of polyaspartates to inhibit the formation of mineral decreased production of oil. Wells can be artificially pres Scale in aqueous Systems. The combined effects of Scale and Surized to force the oil and formation water out of the well, corrosion inhibition in a single additive is a particularly however. In offshore oil platforms, Sea water is pumped into useful feature of polyaspartates. the wells to displace the oil from the formation. The mixture Amide derivatives of long chain amines have been pro of Sea water and formation water that results from this 25 posed as environmentally acceptable corrosion inhibitors in proceSS is referred to as “produced water.” In many cases, oil production applications. See for example Darling, et al., the oil bearing formations have very low levels of dissolved “Green Chemistry Applied to Corrosion and Scale Inhibi oxygen (anaerobic). Often, the formation waters are Satu tors' CORROSION 98, Paper No. 207, National Association rated with dissolved carbon dioxide (known as Sweet wells) of Corrosion Engineers (1998). Unfortunately, such materi with or without dissolved hydrogen sulfide (sour wells), als can be difficult to formulate and can adversely affect the which both result in an acidic pH environment, wherein the oil water Separation process. Thioglycolic acid pH can range from about 3 to about 6. The acidic, highly (mercaptoacetic acid), which is relatively low in toxicity, is mineral laden waters produces an environment that is highly known to be an inhibitor of corrosion. Thioglycolic acid has corrosive to metals, particularly to mild Steel, which is the been used as a corrosion inhibitor in oilfield applications, most common material of construction for well pipe lines 35 however it is only partially effective at inhibiting corrosion and equipment, due to cost considerations. in a carbon dioxide Saturated environment See, for example, Carbon dioxide induced corrosion differs from oxygen U.S. Pat. No. 5,853,619 to Watson et al. induced corrosion in that iron carbonates and other iron Salts There is a need, therefore, for more environmentally are the main corrosion products, as opposed to iron oxide 40 acceptable, biodegradable and low toxicity inhibitors of formation (rust) in aerobic Systems. Mineral Scale formation, metal corrosion in carbon dioxide containing aqueous Sys caused by temperature and pressure changes in the mineral tems where hydrogen Sulfide also may be present. Further, laden formation and especially in produced waters can either there is a need for corrosion inhibitors that are compatible Stimulate or inhibit corrosion, depending on the type and with scale inhibitors and that do not interfere with the physical form of the Scale and the pH, temperature and other 45 oil-water Separation process. The present invention Satis factors. The expense of cleaning and replacing miles of fies these needs. corrosion and Scale damaged pipelines and other equipment on remote oil platforms, and the loSS in revenues from SUMMARY OF THE INVENTION diminished oil production can be enormous. Ferrous metal corrosion in carbon dioxide containing Chemical additives, known as inhibitors, are commonly 50 aqueous Systems can be effectively and efficiently achieved added to prevent the formation of scale and to inhibit the with environmentally acceptable materials. In particular, we corrosion process. The control of Scale and corrosion in have found that amino thiol or amino disulfide compounds offshore oil production has traditionally required complex of the structure: mixtures of corrosion and Scale inhibiting compounds. Many types of corrosion inhibitors are also physically 55 incompatible with scale inhibitors, however. This results in the need to apply these chemicals as Separate treatments. / is i\ is Many classes of chemicals, of widely varying Structures, us- S-Z-S -St. have been used for the inhibition of metal corrosion. See, for R R1 R5 R7 example, reviews on inorganic and organic corrosion inhibi 60 tors by Nathan, “Corrosion Inhibitors’ Kirk-Othmer Ency clopedia of Chemical Technology, 2" Edition, Volume 6, wherein R, R2, R., R., RS, R, R-7 and Rs are, indepen John Wiley & Sons, New York pp. 317-346 (1965) and by dently of one another, members of the group consisting Trabelli, et al. “Mechanism and Phenomenology of Organic of hydrogen, carboxyl, C to C alkyl, and C to Co Inhibitors' Advances in Corrosion Science and Technology, 65 aryl; Volume 1, Plenum Press, New York, pp.147–228 (1970). Z is a member of the group consisting of hydrogen and Many classes of corrosion inhibitors useful in oilfield appli covalent bond; US 6,447,717 B1 3 4 m and n are, independently of one another, 1, 2 or 3; and known in the chemical arts. Thiol functional groups, also p is Zero or 1, with the proviso that p is Zero when known as mercaptains, and primary amine functional groups, Z is hydrogen; in relatively low concentrations are effec can be produced by a variety of known methods. See, for tive inhibitors of ferrous metal corrosion in mildly acid example, methods of production of mercaptains and of aqueous Systems containing dissolved carbon dioxide. amines in Jerry March, Advanced Organic Chemistry, Sec Preferred Such compounds are cysteine, cystine, ond Edition, McGraw-Hill Book Company, New York, N.Y. cySteamine, cyStamine, and Salts thereof. (1977), the relevant portions of which are incorporated The environmentally acceptable corrosion inhibitors of herein by reference. the present invention are useful for the inhibition of ferrous Inhibitors of the foregoing Structure in which m and/or metal corrosion in aqueous Systems that are corrosive due to n=1 may be obtained by the reaction of ammonia with the presence of dissolved carbon dioxide found in oil episulfides or by the reaction of a hydrosulfide ion with producing formations. In oil production terminology, Such aZiridines. aqueous Systems are referred to as "Sweet' for carbon Such inhibitor compounds are generally low in toxicity dioxide containing formations and "Sour” for Systems that and biodegradable.