Effects of pH on Ni-Mn Alloy Deposits on Low Carbon Steel Surface in Acid Enviromnents

The influence of pH of acidic plating solutions on Ni-Mn alloy deposits was studied. The corrosion resistance of Ni-Mn deposits was characterized by EIS and potentiodynamic polarization curves. The micro-hardness of the deposits was also measured and analyzed. The results showed that the Mn content in Ni-Mn alloy deposits and the hardness increased with the increase of pH. When the pH was 5.0, the corrosion current density of the deposit coating was the lowest and the corresponding corrosion potential was relatively high, and under these conditions the coating with a Mn content of 0.84% showed good corrosion resistance. The results of SEM and XRD analyses exhibited that the alloy layer was flat and compact, composed of round cellular particle deposition, and NiMn alloy phase was formed.