Effect of current density on the texture, residual stress, microhardness and corrosion resistance of electrodeposited chromium coating

Textures and residual stresses are generated during electrodeposition of chromium coatings, which directly affect the performance of the coating. In this work, the variations of texture, hydrogen content, residual stress, microhardness and corrosion resistance of chromium deposited from hexavalent [Cr(VI)] chromium bath using direct current deposited technique were investigated. Electrodeposition experiments were carried out on the low carbon steel substrate by varying the key variable current density. The macrotexture of the coatings was studied by XRD. The crystal orientation and dislocation density were analyzed by EBSD. Residual stress was measured by the indentation method. The research demonstrated that a single preferred orientation on the (222) plane was found at current densities of 20 A/dm2, 35 A/dm2 and 50 A/dm2. At 40 A/dm2, a mixed preferred orientation on the (222) + (211) planes was discovered. Furthermore, the formation of the chromium coating texture was affected by the variation of hydrogen content, for higher hydrogen promoting grain growth along the (222) crystal plane. Notably, the microstructure-property relationship was developed. At the single preferred orientation of (222) plane, the corrosion resistance was more favorable. At the mixed preferred orientation of (222) + (211) planes, the coating surface achieved higher microhardness, but formed higher residual stress and more microcracks. Moreover, the better electroplating parameter was proposed. At 35 A/dm2, the coating had the fewer microcracks and the better overall performance. The higher microhardness of 753 HV was found. The more favorable corrosion resistance was discovered, with the breakdown potential and passive current density of 804.7 mV and 2.220 × 10−6 A/dm2. The lower residual stress of 61 MPa was found, which was about 81 % lower than the maximum stress. It was significant in industry for the enhancement of the service life of substrate and the optimization of the chromium coating process.