Introduction of Heavy Micro-Titanium-Carbide Particles into Zn-Ni Coatings on Steel During In Situ Brush Electroplating

The heavy micro-titanium-carbide (TiC) particles are first introduced into brush-electroplated Zn-Ni coating (TiC-0 coating) by using some surfactants here. The effect of TiC concentration of brush-electroplating solution on the properties of Zn-Ni-TiC coatings is investigated. It is found that the coating hardness and corrosion resistance are enhanced significantly due to the co-deposition of TiC and an optimal coating with a thickness of 71 mu m and adhesive strength of 37.2 MPa is obtained when TiC concentration was 40 (g L-1) (TiC-40 coating). The pencil hardness of TiC-0 and TiC-40 is 2 H and 5 H, respectively. The corrosion resistance time to hot NH4NO3 solution (or inferred neutral salt spray) of TiC-0 and TiC-40 are 40 and 240 min (or 321 and 1995 h), respectively. Many pores appear on the coating due to the incomplete overlap of many batch layers. The TiC content is the factor dominating the coating hardness and corrosion resistance by changing the structure, contact angle, and pore diameter of coating, thereby changing the linear polar resistance Rp from potentiodynamic polarization curves, charge-transfer resistance Rct or |Z|0.01 Hz, or polarization resistance from electrochemical impedance spectroscopy. The content of Zn-Ni alloy is the factor dominating the adhesive strength of Zn-Ni-TiC coating. Although many Zn-Ni-X (X = carbides or oxides) electroplating coatings have been reported, Zn-Ni-TiC coating has never been reported so far, considering TiC particles are more heavy in density than usual X and thus are difficult to suspend in electroplating solutions. The heavy micro-TiC particles are successfully introduced into smooth-brush-electroplated Zn-Ni coating with the aid of some surfactants here.image (c) 2023 WILEY-VCH GmbH