Effects of current density, coating thickness, temperature, pH and particle concentration on internal stress during Ni–MoS₂ electrocodeposition

Internal stress in plated deposits has been a common problem that may affect the functionality of coatings. Electrodeposition parameters and insoluble particles modify the characteristics and the level of internal stress of coatings. The influence of the electrocodeposition parameters and their interaction effects on the internal stress during the electrodeposition of Ni and Ni–MoS₂ composite coatings were studied by fractional factorial design. The parameters studied and their ranges were: MoS₂ particle concentration (0–10 g L⁻¹), temperature (30–50°C), pH (2–4), current density (1·2–4·8 A dm⁻²), and coating thickness (25–50 μm). MoS₂ addition into Watts bath resulted in the decrease in the tensile internal stress values or even changed the stress character from tensile to compressive. Moreover, low stress values were obtained when pH was 2 and coating thickness was 50 μm.