ステンレス鋼銀ろう付部の腐食機構について

概要

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The corrosion behaviour of silver brazed SUS 304 stainless steel in sodium chloride solutions with the additions of cupric chloride has been investigated using electrochemical and metallographic techniques. The interfacial corrosion mechanism was discussed in relation to the polarization behaviour of SUS 304. The cause of the interfacial corrosion of stainless steel was found to be attributable to the removal of corrosion resistant passive oxide films on stainless steel during brazing by brazing flux, because the anodic reaction was enhanced by the flux treatment. The interfacial corrosion could be penetrated along the narrow and less corrosion resistant zone between filler and stainless steel. Preferentially dissolved zinc and copper from α-Cu phase precipitated as chlorides on the specimen surface. The added copper in corrosive solution enhanced the corrosion rate by accelarating the cathodic reaction of both stainless steel and filler alloy. The precipitation of the metallic copper produced by cathodic reduction was occurred on the cathodic site such as α_1-Ag phase of filler alloy and stainless steel surface. The pH change during the immersion test was thought to be caused by the precipitation of added copper and the dissolution of iron, zinc and other alloying elements.
1980-05-05