Localised corrosion of highly alloyed stainless steels in an ammonium chloride and diethylamine chloride aqueous solution

Abstract

This paper studies the pitting corrosion of highly alloyed stainless steels (SS) immersed in an ammonium chloride and diethylamine chloride aqueous solution at temperatures of 25, 40, 60 and 80°C. Four materials were tested: UNS S 31726 SS, UNS S 31254 SS, UNS S 32550 SS and titanium, for comparative purposes. Gravimetric, after immersion up to 103 days, polarisation curves, impedance. SEM, EDX and optical microscopy were the techniques used. UNS S 31726 SS shows the lowest corrosion resistance. UNS S 31254 and UNS S 32550 SSs show similar behaviour. Titanium presents impedance data three orders higher than the other SS materials. The SS materials present a pseudoinductive behaviour on impedance data, associated with an adsorption process of the amine compound which decreases as the temperature increases.