Corrosion Behavior of Low Alloy Steel And 700mpa Grade Ni, Cr Composite Weathering Steel in Simulated Marine Atmospheric Environment

Abstract

The dry-wet cycle corrosion behavior of low alloy steel (Q355B) and 700MPa grade Ni, Cr composite weathering steel (4 wt.% Ni-5 wt.% Cr) in 2 wt.% NaCl solutions was studied. The distribution characteristics of elements and phases in the corrosion products after 360h corrosion cycle were analyzed by SEM and Raman spectroscopy. The formation mechanism of protective rust layer of Ni, Cr composite weathering steel in simulated marine environment was briefly described. The results show that the corrosion products of Q355B appear obvious stratification, and the rust layer of Ni, Cr composite weathering steel has no longer stratified. The Ni, Cr composite weathering steel forms a cationic selective rust layer during the corrosion process, which effectively prevents the penetration of Cl- and exhibits excellent corrosion resistance, the corrosion rate of Ni, Cr composite weathering steel after 72h-360h corrosion cycle is 1/8-1/3 of that of Q355B. The value of α/γ* increases with the extension of corrosion cycle, which is reach to 1.0 after 360h corrosion cycle. The corrosion potential increases with the extension of corrosion cycle, the corrosion current density fluctuates slightly around 100×10-6 A/cm2.

Keywords: Ni, Cr composite weathering steel, NaCl solution, cation selectivity, rust layer, electrochemical behavior