Plasma electrolytic oxidation of cold-drawn steel wire: Optimising current density for enhanced corrosion resistance without compromising tensile strength

To resolve corrosion degradation issues of cold-drawn high-carbon steel wires in marine engineering, plasma electrolytic oxidation (PEO) treatment was conducted at controlled current densities, with their influences on microstructural features, corrosion resistance and mechanical performance examined. Corrosion resistance increases monotonically with the increments in current density, achieving an 11.7-fold higher total resistance (∼41.2 kΩ cm 2 ) at 0.19 A/cm 2 versus bare steel wire (∼3.5 kΩ cm 2 ). At 0.22 A/cm 2 , even though the total resistance peaks at ∼46.6 kΩ cm 2 , the intense plasma discharge induced substrate cracking, causing ∼15.3 % tensile strength loss and ∼18.4 % elongation reduction. The PEO process was therefore optimised at 0.19 A/cm 2 , simultaneously retaining 99.9 % tensile strength and 97.9 % elongation of the steel wire while delivering maximised corrosion protection.