Patent ID: 6974553

Claim:
A method of inhibiting corrosion of metals in contact with an aqueous alkanolamine solution in an acid gas removal amine unit comprising adding to the aqueous alkanolamine solution an effective corrosion inhibiting amount of a polythiaether compound having the formula: G 1 -Z′-(R″—S) n —R—(S—R′) m -Z-G and their appropriate salts with mineral acids, wherein n=1-10; m=1-10; R is C2-C12 linear or branched alkyl; aryl optionally substituted with C1-C6 alkyl, halogen, C1-C4 alkoxy, NR 3 R 4 , phenyl, nitro, cyano, COOR 3 , OCOR 4 wherein R 3 , R 4 are independently H, C1-C4 alkyl, phenyl; C4-C10 heterocyclic; C7-C10 alkylaryl; or C—[(CH 2 )—] 4 , provided that when R is C—[(CH 2 )—] 4 , each of the four CH 2 is independently bonded through the S atom to the same or different —(S—R′) m -Z-G or G 1 -Z′-(R″—S) n — groups; R′ and R″ are independently C2-C12 linear or branched alkyl; aryl optionally substituted with C1-C6 alkyl, halogen, C1-C4 alkoxy, NR 3 R 4 , phenyl, nitro, cyano, COOR 3 , OCOR 4 wherein R 3 , R 4 are independently H, C1-C4 alkyl, phenyl; C4-C10 heterocyclic; C7-C10 alkylaryl; Z and Z′ are independently S, O, NR 5 , COR 6 ; G and G 1 are independently H; methyl; R′; R″; (CH 2 CH 2 NH) r H, wherein r=0-100; R 5 =H; C1-C8 alkyl; (CH 2 CH 2 NH) r H, r=0-100; R 6 =NR 3 R 4 ; OR 7 wherein R 7 =H, C1-C4 alkyl, phenyl; OM wherein M=Na, Li, K; and when Z=NR 5 , G or G 1 and R 5 together with nitrogen form cyclic amines comprising piperazines, morpholines, or piperidines.