CORROSION OF STAINLESS STEELS IN CONTAMINATED SULFAMIC ACID, 2012 TAPPI PEERS Conference

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A comparative study of several industrial relevant stainless steels exposed in 10 wt. % sulfamic acid, NH2HSO3, with 15 ppm chlorides is presented in this paper. Non-welded coupons of austenitic grades EN 1.4307 (S30403), 1.4404 (S31603), lean duplex grades 1.4162 (S32101), 1.4062 (S32202), 1.4362 (S32304) and duplex grades 1.4662 (S82441) and 1.4462 (S32205) were tested. Experiments were performed in double-wall reactor beakers with 10 wt. % NH2HSO3, with 15 ppm chlorides at 80 °C. Tests were performed both in stagnant and non-stagnant conditions, circulation held with a magnetic stirrer at 600 rpm. Coupons were immersed for a total time of 168 h, with periods divided into 24 hours, 72 hours and activated prior to the last 72 hours exposure in order to evaluate the ability for material repassivation. Weight loss and thereby corrosion rates were established for all the stainless steel grades. The materials were evaluated on localized corrosion effects after exposure with light optical microscope (LOM). All grades were observed to be corrosion resistant in uninhibited 10 wt. % NH2HSO3 with 15 ppm chlorides at 80 °C, i.e. showed a corrosion rate below 0.1 mm/y.