Electrolytic production and characterization of nickel–rhenium alloy coatings

Jolanta Niedbała,Dorota Kopyto,Andrzej Szymon Swinarew,Magdalena Popczyk,Izabela Matuła

doi:10.1515/rams-2021-0058

Abstract

Abstract Electrolytic Ni–Re alloy coatings were obtained in galvanostatic conditions from nickel–rhenium baths with different contents of ammonium rhenate(vii) (0.5, 1.25, 2.5 and 5 g·L−1). The surface morphology, chemical, and phase composition of the obtained materials were determined. The coatings’ corrosion resistance tests were carried out in a 5% NaCl solution. Based on the tests, it was found that the highest corrosion resistance characterizes the coating with the highest rhenium content (37%). This material can be recommended for practical use as a protective coating. The density of the deposited Ni–37Re alloy was determined, and its specific surface area was assessed. The melting point, hardness, and electrical conductivity were also determined.

Highlights

The top layer formed in the technological process may have a positive effect on the functional properties of the materials, e.g., wear and corrosion resistance, fatigue strength, etc
The specified efficiency of the electrochemical deposition of Ni–Re alloy coatings was in the range of 95–99%
The analysis of the chemical composition of the Ni–Re alloy coatings performed using the X-ray fluorescence spectrometry (XRF) method showed that the average rhenium content in the coatings ranges from 18.7 to 37.0% and increases with the increase of ammonium rhenate(VII) in the plating bath (Figure 1)

Summary

Introduction

The top layer formed in the technological process may have a positive effect on the functional properties of the materials, e.g., wear and corrosion resistance, fatigue strength, etc. Such a coating is harder than the substrate. In Wen’s work, he characterized the dependence of the rhenium content in the alloy coating on the pH of the plating bath extensively, determined the mechanical properties and the influence of temperature on the obtained rhenium coatings. The coatings were obtained from a bath containing nickel(II) sulfate, potassium rhenate(VII), and citrate ions. Rhenium-containing alloys were tested for their corrosion resistance. The three-component CoWRe coating was characterized by the highest value of corrosion resistance and microhardness

Methods

Results

Conclusion