Zincating Effect on Corrosion Resistance of Electroless Ni‐P Coating on Aluminum Alloy 6061

Abstract

Aluminum and its alloys represent a promising alternative as bipolar plates in proton exchange membrane fuel cell (PEMFC) systems. However, to improve the corrosion resistance they are commonly coated, and electroless Ni‐P offers great advantages. The effect of multiple zincating process on the corrosion behavior of electroless Ni‐P coatings on AA6061 was investigated. Results of morphological characterization and compositional analysis of the electroless Ni‐P coatings showed that as the number of zincating steps increased, the surface became smoother (with decreasing roughness) and the phosphorous content increased. The results of electrochemical impedance measurements and potentiodynamic polarization curves in 0.5M H2SO4 solution showed that the pretreatment used before coating of aluminum with Ni‐P has a direct effect on corrosion resistance. The corrosion current density decreased with increasing the number of zincating steps. A significant improvement in corrosion resistance was observed on performing the triple zincating.

Metallic Material Selection and Prospective Surface Treatments for Proton Exchange Membrane Fuel Cell Bipolar Plates—A Review

“…A negative effect of copper on corrosion properties was also observed for pre-galvanized aluminum alloys, Ni-Co-P [46] and Ni-P coated aluminum alloys [160], where higher phosphorus content is desirable in order to achieve higher amorphous structure and better corrosion properties. In addition, repeated zinc plating makes it possible to achieve a better morphology of the N-P coating on galvanized aluminum 6061 and a lower corrosion rate of 4.4 µA•cm −2 , but the resistance properties were not measured [161]. Ni-P-Cr was prepared on AA 7075-T6 and consisted of 20 µm Ni-P interlayer with 10 µm of electroplated Cr.…”

Electroless Ni-P-MoS2-Al2O3 Composite Coating with Hard and Self-Lubricating Properties

“…Typically, the corrosion resistance of the EL-plated components depends on the degree of crystallinity, P content, phase change, coating thickness, porosity on the surface, size, and orientation of grains [ 19 , 20 , 21 ]. As per a study by Gutierrez et al, the corrosion resistance of the Ni-P EL-coated component depends upon the P content, the extent of internal stress, and the amorphous state [ 22 ]. The performance evaluation of Ni-P coated surfaces has been conducted in the context of the factors mentioned above in several studies [ 8 , 9 , 10 ].…”

Effect of rare earth on microstructure and corrosion behavior of electroless Ni-W-P composite coatings

“…Various surface modification techniques for the preparation of alloy coatings have been implemented as common methods such as physical vapor deposition (Cui et al , 2021; Vannozzi et al , 2018), electrodeposition (Zhang and Zhang, 2019; Mahalingam and Bera, 2020; Ma et al , 2020) and electroless plating (Wang et al , 2020; Shi et al , 2017). Among all technologies, electroless plating of Ni-P alloy coatings was preferred because of the low cost and unique preparation advantages (Shu et al , 2019; Li et al , 2019; Gutierrez et al , 2017). Numerous transition metals for example Mn (Jiang et al , 2019), Fe (Yang et al , 2019), Cu (Wang et al , 2020; Chen et al , 2017), Mo (Rosas-Laverde et al , 2020), Co (Sarika et al , 2021) and W (Tian et al , 2021; de Oliveira et al , 2018) have been reported in many publications, which have been used to broaden the performance of electroless Ni-P coatings.…”