2000 Volume 49 Issue 5 Pages 294-300
The present study is concerned with the construction of aqueous chemical potential diagrams of multiple metallic elements systems and the interpretation of the equilibrium diagrams to the effect of alloying elements on the stabilization of rust of weathering steels. Among chemical potential diagrams, our attention is focused on E-pH diagrams of bimetallic systems. In the corrosion process of weathering steels it is recognized that stabilization of rust proceeds accompanying the coprecipitation or sorption of minor elements to ferric hydroxide. Since the data are scarce for stability of aqueous reaction the tendency for the coprecipitation and sorption were estimated on the analogy of complex oxide formation based on the high temperature thermodynamical data. New E-pH diagrams of bimetallic systems led to a conclusion that elements beneficial for weathering steels are those forming insoluble complex oxide with iron at relatively low pH. A clear correlation exists between tendencies of complex oxide formation and of coprecipitation and sorption with rust.
