The effect of current density and bath temperature in the electroplating process on resistance to corrosion of Zn-Ni alloys was evaluated in this work. The electrolytic bath consisted of nickel sulfate, zinc sulfate, sodium sulfate, boric acid, and sodium citrate at pH 7.0. The current density was varied in the range 20–80 mA/cm² and the bath temperature in the range 30–60 °C. Increasing, independently, the current density or the bath temperature increased the nickel content in the obtained alloy, which affected the alloy microstructure, with a predominant γ phase and cauliflower-like morphology. The nickel content in the alloys was in the range 20–42%wt. A synergistic effect between the current density and bath temperature was observed from a design of experiments and response surface models. The maximum resistance to corrosion occurred for the alloy containing 42%wt. nickel. This alloy was obtained at upper levels of current density and bath temperature, presenting a corrosion potential of −0.789 V and polarization resistance of 4136 $\mathsf{\Omega }$.cm².

Foram avaliados os efeitos da densidade de corrente e agitação mecânica do banho no processo de eletrodeposição para obtenção da liga Zn-Ni. Foi utilizado um banho eletrolítico constituído de sulfato de níquel, sulfato de zinco, sulfato de sódio, ácido bórico e citrato de sódio em pH 7,0. A densidade de corrente foi avaliada na faixa de 10-50 mA/cm² e para a agitação mecânica foi avaliada na faixa de 30-70 rpm. Como ferramenta de otimização, foi utilizado um planejamento fatorial completo 2² com três elementos centrais associado à Metodologia de Superfície de Resposta (MSR). Foi observado que o aumento da densidade de corrente e da agitação mecânica provocou o aumento do percentual atômico de níquel nos revestimentos. O percentual de zinco aumentou com a diminuição da densidade de corrente. O ponto ótimo de níquel obtido foi de 39 at.%. A eletrodeposição foi do tipo anômala. A microdureza aumentou com o aumento do percentual de níquel e com a diminuição do percentual de Zn no revestimento. Os revestimentos apresentaram nódulos na superfície com diferentes tamanhos e formas.

This study aims to manufacture and characterize titanium and nickel alloys with different molybdenum (Ti–Ni–Mo) contents, focusing on the influence of these additions on the microstructure, mechanical properties, and corrosion resistance. The relevance of this work stems from the lack of research on this specific alloy and the absence of reports in the literature with molybdenum percentages above 2 at.%. Ti₅₀Ni_50−XMo_x alloys were produced by the plasma arc melting method, with six different compositions (x = 0, 0.5, 1, 2, 3, and 4 at.% Mo), and a comprehensive analysis of microstructure, chemical composition, thermal, mechanical, and electrochemical properties was carried out. The results demonstrated significant alterations in the microstructure of the Ni–Ti alloy with the addition of molybdenum presenting several phases, precipitates (TiNi, Ti₂Ni), and oxides (Ti₄Ni₂O, TiO, and TiO₃). The stability of the B2 phase increased with molybdenum content, and the monoclinic martensite (B19′) phase was identified only in the Ni–Ti sample. Introducing molybdenum into the Ni–Ti alloy generated the R-phase and shifted the phase transformation peaks to lower temperatures, as differential scanning calorimetry (DSC) indicated. Microhardness and elastic modulus decreased with increasing Mo content, ranging from 494 HV to 272 HV and 74 GPa to 63 GPa, respectively. Corrosion tests revealed increased corrosion resistance with increasing Mo content, reaching a polarization resistance of 2710 kΩ·cm² and corrosion current of 11.3 µA. Therefore, this study points to Ti–Ni–Mo alloys as potential candidates to increase the range of Ni–Ti alloy applications, mainly in biomaterials, reinforcing its relevance and need in current alloy research.