Localized corrosion resistance of stainless steel (Type 316L), a titanium-based alloy (Ti-0.15Pd) and corrosion-resistant nickel-based alloys (a new alloy MAT-21 (Alloy T) and Alloy C-276) was evaluated in four simulated seawater solutions containing 1.8 to 22.0 wt% of chloride ions concentrated by evaporation. Stress corrosion cracking was observed on the 316L stainless steel but not on Alloy T and Alloy C-276 in the solutions. Pitting attack occurred on the surface of the 316L stainless steel base metal in all the solutions. Alloy C-276 suffered pitting attack on the surface including the welded section only in the solutions containing 18.9 and 22.0 wt% of chloride ions, respectively. No pitting attack occurred over any part of the surface including the welded section of Alloy T in any of the solutions. No crevice corrosion was observed in an immersion test of Alloy T and the Ti-0.15Pd alloy using test pieces with crevices although crevice corrosion was seen the creviced test pieces of Alloy C-276 and the 316L stainless steel. It was found that both Alloy T and the Ti-0.15Pd alloy, which exhibit high repassivation potentials for crevice corrosion (ER,CREV) corresponding to crevice corrosion potentials, have excellent crevice corrosion resistance, while these alloys which exhibit corrosion potentials greater than ER,CREV in a solution with a high chloride ion concentration and a high dissolved oxygen concentration in open air may be corroding in the crevices.

Subject
Steel surfaces, Corrosion resistant alloys, Stainless alloys, Repassivation potentials, Chloride solutions, Base metals, Crevices, Crevice corrosion, Pitting, Corrosion resistance, Stainless steel, Titanium alloys, Corrosion potential
Keywords:
Nickel based alloy, stainless steel, titanium, chloride, seawater, salt, crevice corrosion, pitting
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1998
Association for Materials Protection and Performance (AMPP)
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