Effect of Electrolyte pH on Microstructure, Corrosion Behavior, and Mechanical Behavior of Ni-P-W-TiO2 Electroplated Coatings

Ni-P-W composite coatings are resistant to wear and corrosion. TiO 2 particles are used as a reinforcing phase in the matrix of alloy coatings for abrasive applications. In this study, Ni-P-W-TiO 2 coating was precipitated on the AISI 304L steel substrate using an electroplating method. Electroplating was performed at pH levels of 1, 2, and 3, and the effect of bath pH on microstructure, corrosion behavior, and wear behavior was investigated. The coatings were characterized by scanning electron microscopy. In order to investigate corrosion resistance, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests were used in 3.5 wt.% NaCl aqueous solution. The mechanical behavior of the coated samples was investigated by examining wear resistance and micro-hardness. The results of potentiodynamic polarization and EIS tests demonstrated the coating formed at pH = 2 had the highest corrosion resistance (7058 Ω cm 2 ) compared to the coated sample at pH = 1 (57 Ω cm 2 ) and pH = 3 (10.59 Ω cm 2 ). Also, the results of the wear and micro-hardness test showed composite coating formed at pH = 2 had the highest wear resistance and micro-hardness (677 Vickers) compared to the coated sample at pH = 1 (403 Vickers) and pH = 3 (511 Vickers).