Chloride-induced corrosion behavior of cold-drawn pearlitic steel wires

Abstract The chloride induced corrosion behavior of cold drawn pearlitic steel wires was systematically investigated using electrochemical measurements, namely, electrochemical impedance spectroscopy, and local electrochemical impedance spectroscopy for micro-areas. A 0.05 mol/L NaCl solution mixed with borate buffer solution (pH = 8.45) was used. The results suggest that the corrosion resistance of cold-drawn pearlitic steel decreases with increasing strain to 0.8, but increases with strain up to a value of 1.6. Microstructure evolution was characterized by electron back scatter diffraction in combination with scanning electron microscopy and transmission electron microscopy. Atom probe tomography was used to quantify the cementite decomposition. The quantitation of microstructural parameters with strain suggests that the evolution of defect structure markedly increases the corrosion susceptibility of pearlite for strain up to 0.8. In the case of strain 1.6, refinement of the lamellar structure and cementite decomposition can reduce the volume fraction of cementite that acts as the cathode per corrosion unit (a pearlite/cementite “cell”), giving rise to an increase in the corrosion resistance.