Inhibition of Pitting on a Type 316L Stainless Steel Acetic Acid Tank
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Various preventive measures including cathodic protection were tested in the laboratory. The preventive measure applied was to remove the inhibitor from the acid blend. The attack proceeds in the HAZ immediately adjacent to the weld and follows an intergranular pattern. The weld deposit itself shows less damage but is not completely unattacked, with some weld undercutting observed. The pitting tendency is ameliorated by a relatively high repassivation potential, which should aid in repassivation of any pits that form. The results indicate that the green acid blend is more aggressive in terms of the pit propagation rate. This behavior also is consistent with a lower pitting potential than what can be expected in the red acid. The cathodic protection (CP) scenario was evaluated considering that due to operating conditions no contamination with cations in acid solution is acceptable since that could bring scaling problems downhole in the producing wells.
author list (cited authors)
Case, R. P., & McIntyre, D. R.