PITTING CORROSION BEHAVIOR OF TYPE 904L STAINLESS-STEEL IN SODIUM-BROMIDE SOLUTIONS

Potentiodynamic cyclic anodic polarization, scanning electron microsco py (SEM), and energy dispersive x-ray (EDX) techniques were used to st udy pitting corrosion behavior of type 904L (UNS N08904) stainless ste el (SS) in aerated or argon-deaerated 0.6 M sodium bromide (NaBr) solu tions at 25 degrees C. Type 904L SS was shown to undergo pitting corro sion even though the steel has a high molybdenum content (4.5% Mo). Ef fects of temperature, air, pH, bromide ion concentration (C-Br(-)), an d bromide/chloride ratio on pitting corrosion were studied. The critic al pitting potential (E-pit) was found to decrease with increasing tem perature and C-Br(-). Changing the pH of the 0.6 M NaBr solution did n ot affect E-pit from pH 2 to 11. At pH greater than or equal to 12, pi tting corrosion was prevented. Addition of chloride ions to bromide at a fixed halide concentration of 0.6 M inhibited pitting corrosion att ack. Morphology of the pits produced was inspected by SEM after anodic polarization treatment in different bromide solutions.