Effect of P Content on the Corrosion Behavior of Electrodeposited Fe-P Coatings

Abstract

Eco-friendly Fe-P coatings containing different P contents up to 20wt% were electrodeposited on pure copper substrate. Scanning electron microscopy, grazing incident X-ray diffraction, microhardness, electrochemical impedance spectroscopy, and potentiodynamic polarization tests were used to investigate the effect of P content on the microstructure and corrosion behavior of the coatings in 3.5 wt% NaCl solution. Results showed that the surface becomes smoother with increasing the P content and superficial microcracks form at 20 wt% P. Coatings containing 5 and 10 wt% P showed a nanocrystalline microstructure, while a fully amorphous microstructure obtained at higher P contents. The best corrosion resistance was seen for the coatings containing 10 and 15 wt% P, which was related to their microstructure and smooth surfaces. Defect-free Fe-P coatings can increase the corrosion resistance of the copper and have the ability to protect the substrate through galvanic effect in which the coating acts as the anode. The coating hardness revealed an inverse Hall-Petch relationship so that the hardness of the coating decreased with decreasing the crystallite size of the deposit.

Modelling and Optimization of Electrodeposited Amorphous Fe-P Alloys Using CCC Design and RSM

“…Figure 2(c) shows the XRD pattern with a distinct diffuse peak at approximately 2θ = 45°, con rming the amorphous structure of the sample. The bath composition and operating conditions impact the nucleation sites and nuclei growth rate, which regulate the surface nodularity [11]. Figure 2(d) shows a smooth coating surface with an average roughness (R a ) of 0.070 µm and a root mean square roughness (R q ) of 0.116 µm.…”

“…The composition and operating parameters of a bath can be adjusted to obtain the targeted chemical composition, phase structure, microstructure, and properties [2,[10][11][12]. The main salt concentration dominates the chemical composition, deposition rate and roughness [13].…”

“…In addition, the deposit is amorphous when the P content is greater than 8 wt.%. To date, numerous researchers have employed single-factor and orthogonal experiments to study the impacts of different amorphous Fe-P electrodeposition process parameters on the behaviours and properties of deposits [10,11,22,23]. However, there is a lack of quantitative studies on the correlations among parameters, P contents and deposit properties.…”