The corrosion behavior of Ni–P deposits with high phosphorous contents in brine media

The corrosion behavior of Ni–P deposits with the phosphorous contents of 20, 24 and 28 at.% (denoted as Ni–20P, Ni–24P, and Ni–28P, respectively) and annealed in air at different temperatures was systemically compared in a brine medium containing 3 wt.% NaCl. The anticorrosive properties of these Ni–P deposits were further examined in a brine-fog test (using a 5 wt.% NaCl solution) under 37 °C for 24 h. In the electrochemical studies, the Ni–28P deposit showed the lowest corrosion rate when it has been annealed between 200 and 300 °C. This deposit also exhibited the highest corrosion resistance in the studies of linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). In the brine-fog study, the weight loss of the Ni–P deposits was found to decrease with increasing the phosphorous content. After the brine-fog test, there was no obvious change in morphologies for all Ni–P deposits with the annealing treatment at 300 °C.