Excellent Properties of Ni-15 wt.% W Alloy Electrodeposited from a Low-Temperature Pyrophosphate System

Changwei Su,Linfu Zhao,Wei Bai,Fengjing Wu,Yangyang Liu,Zhaoyao Sa

doi:10.3390/coatings11101262

Changwei Su, Linfu Zhao + Show 4 more

Open Access

https://doi.org/10.3390/coatings11101262

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Abstract

Electrodeposited Ni-W alloy coatings are considered to be one of the most suitable candidate coatings to replace carcinogenic hexavalent chromium coatings. In this work, Ni-W alloys are electrodeposited from pyrophosphate baths containing different concentrations of Na2WO4 2H2O (CW) at 40 °C. Both CW and the applied current density can affect the W content in the coatings. The effect of CW becomes weaker with the increased current density. The Ni-W alloys with 15 ± 5 wt.% W (Ni-15 wt.% W) are obtained from the bath containing 40 g L−1 CW at a high current of 8 A dm−2. The microhardness, corrosion resistance and hydrogen evolution reaction (HER) are measured with a microhardness tester and an electrochemical workstation. The modified properties are studied by heat treatment from 200 to 700 °C. The highest microhardness of 895.62 HV and the better HER property is presented after heat treatment at 400 °C, while the best corrosion resistance in 3.5 wt.% NaCl solution appears at 600 °C.

Highlights

With the development of science and technology, the corrosion resistance and other performance requirements of materials are continuously improved [1]
Ni-W alloy coatings were prepared by electrodeposition in a lowtemperature pyrophosphate bath and their corrosion resistance and hydrogen evolution reaction (HER) properties were studied in detail
The compact and flat Ni-15 wt.% W alloy without cracks was electrodeposited from a pyrophosphate system at 40 ◦C and presented a high microhardness, excellent oxidation resistance, excellent corrosion resistance and good HER activity

Summary

Introduction

With the development of science and technology, the corrosion resistance and other performance requirements of materials are continuously improved [1]. The Ni-W electroplating layer is considered to be one of the candidates to replace hard chromium plating due to its smooth surface, high hardness, excellent wear resistance, good corrosion resistance and low cost. It is widely used in the protective coating of glass membranes, hydraulic parts and valves [10]. Ni-W alloy coatings were prepared by electrodeposition in a lowtemperature pyrophosphate bath and their corrosion resistance and HER properties were studied in detail. The organic chelating agents, such as citric acid, were usually added into baths to obtain Ni-W alloys with good wear and corrosion resistance [19]. The pyrophosphate chelating agent was selected in this work

Electrodeposition of Ni-W Alloys

Characterization

Electrochemical Measurements

Conclusions