Galvanic Corrosion Behaviors of A508-III/304L Couples in Boric Acid Solution

摘要

Alloy 508-III steel and 304L stainless steel are often used in pressure vessels found in nuclear powerplants, and when both are exposed to boric acid, galvanic corrosion will occur and affect operationalsafety. The corrosion behavior and galvanic corrosion behavior after pairing these two metals in differentboric acid solutions were studied by open circuit potential, polarization curve, AC impedance, zero-resistance ammeter, weight loss and SEM methods. The results showed that the differences inelectrochemical properties between the two metals made A508-III act as the anode and 304L act as thecathode to form a galvanic couple that promoted the occurrence of galvanic corrosion. Compared witha single corrosive environment, the corrosion rate of A508-III was significantly accelerated undergalvanic corrosion and the surface oxide composition also changed. An increase in the concentration ofboric acid solution exacerbated galvanic corrosion. An excessive anodic area could slow down thegalvanic corrosion current and quickly stabilize the corrosion. Ultimately, a galvanic corrosion model ofA508-III and 304L in boric acid solution was described.