The present study involved the evaluation of selected stainless and nickel base alloys in the following acidizing media: (1) 15 percent HCl, (2) 28 percent HCl, (3) 12 percent formic acid and (4) 13 percent HCl/2 percent HF. Tests were conducted both with H2S and with CO2 at 200 F and 400 F. Two different inhibitors were used in each acidizing media. Acidizing media were generally found to be very aggressive to stainless and nickel base alloys. In most cases, the 22 Cr and 25 Cr duplex stainless steels exhibited selective attack of the ferrite phase by the acid solutions. However, under most conditions, corrosive attack was of a general nature with pitting occurring in only a few cases. Isolated occurrences of intergranular corrosion and end grain attack were noted. A method of determining compatibility of high alloy materials with acidizing media is presented based on the following guidelines: (1) general weight loss corrosion rate of <2000 mpy, (2) low tendency for localized corrosion, and (3) no stress corrosion cracking.
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