Corrosion Mechanism of Silver Brazed Stainless Steel Joint in Chloride Solutions(Materials, Metallurgy, Weldability)
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Electrochemical and metallographic studies have been made on the silver brazed SUS 304 stainless steel joint to demonstrate the interfacial corrosion mechanisms in sodium chloride solutions with additions of cupric chloride. The corrosion behaviours of silver brazed stainless steel joints have been investigated as functions of pH, cupric chloride concentration and composition of filler alloy. Polarization measurements revealed that the removal of corrosion resistant passive films on stainless steel by brazing flux during brazing was one of the causes of interfacial corrosion of stainless steel at brazed interface. Formation of nickel depleted zone in SUS 304 at brazing interface also appeared to be responsible to the cause of interfacial corrosion. The added copper to corrosive solution enhanced the cathodic reaction of both stainless steel at brazed interface and filler alloy. As a result of cathodic reduction, metallic copper precipitated on cathodes such as α_1-Ag phase of filler alloy and bulk stainless steel surface. Preferential dissolved zinc and copper from α-Cu phase adhered as chlorides to specimen surface. The pH change of corrosive solution during immersion test appeared to be caused by precipitation of added copper, dissolution of iron, zinc and other alloying elements.
- Transactions of JWRI
Transactions of JWRI 9(2), 217-223, 1980-12