SYNERGISTIC EFFECT OF Cu AND Ni ON ATMOSPHERICCORROSION RESISTANCE FOR LOW-ALLOYING STEELIN WET/DRY CYCLIC ENVIRONMENTS

摘要

The atmospheric corrosion performance of mild steel, 0.3%Cu-bearing steel, 1%Ni-bearingrnsteel, 4%Ni-bearing steel, 0.3%Cu-1%Ni-bearing steel and 0.3%Cu-4%Ni-bearing steel (CuNi-alloying)rnwere studied by dry/wet cyclic corrosion tests (CCT) at 30 ℃ and 60% relative humidity (RH),rnrespectively. The corrosive solutions used for CCT were 0.3 mass% NaCl solutions. The gravimetryrnresults showed that rusted steel of CuNi-alloying presented synergistic corrosion resistance comparedrnwith others rusted steels. Electrochemical impedance spectroscopy (EIS) showed that CuNi-alloyingrnfacilitated the uniform corrosion at the initial stage and enhanced the compactness and stabilization ofrnrust layer after corrosion. Polarization curves indicated that CuNi-alloying depressed both cathodic andrnanodic reactions at the initial stage, while accelerated the cathodic reduction of rust after a rust filmrnformed on steel. The XRD and SEM results demonstrated that the addition of CuNi improved therncorrosion resistance of steel by delaying the crystallization of rust and changing the composition of rust.rnTherefore, the synergistic effect of CuNi-alloying came from the amelioration of the protectiverncompact rust layer on steel.