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Effects of blackening parameters on the formation and adhesion of oxide on AISI 4140 steel

Somrerk Chandra-ambhorn (Department of Materials and Production Technology Engineering, King Mongkut’s University of Technology North Bangkok, Bangkok, Thailand)
Sermsak Srihirun (Department of Materials and Production Technology Engineering, King Mongkut’s University of Technology North Bangkok, Bangkok, Thailand)
Thamrongsin Siripongsakul (Department of Materials and Production Technology Engineering, King Mongkut’s University of Technology North Bangkok, Bangkok, Thailand)

Anti-Corrosion Methods and Materials

ISSN: 0003-5599

Article publication date: 11 June 2018

Issue publication date: 24 July 2018

107

Abstract

Purpose

The purpose of this study is to investigate the aesthetic blackening coating formed by a hydrothermal process, focusing on the formation of magnetite and the oxide adhesion for improving the corrosion resistance of the steel.

Design/methodology/approach

The aesthetic black coating was applied on AISI 4140 steel using a hydrothermal process with a non-toxic solution consisted of ferrous sulphate hydrate (FeSO4·7H2O), sodium hydroxide (NaOH) and hydrazine hydrate (N2H4·H2O). Upon process parameters temperature and time, the morphology of the coatings and oxidation kinetics were investigated by using scanning electron microscopy and X-ray diffraction (XRD) analysis. Furthermore, the samples with coatings were subjected to the adhesion test using a tensile testing machine equipped with a charge-coupled device (CCD) camera.

Findings

From the formation parameters due to temperature and time for the conversion coatings, it was found that the oxidation kinetics had special characteristics which were in accordance with a linear rate law and Arrhenius relation. For the samples blackened, the XRD analysis results revealed that the magnetite was successfully formed on the surface of the steel. On the other hand, increasing the blackening temperature worsened the scale adhesion as observed by the lower strain provoking the first spallation and the higher sensitivity of the oxide to spall out with the imposed strain.

Originality/value

The effects of parameters of the formation of conversion coatings were investigated to understand the kinetics of the coatings. Furthermore, a tensile adhesion test using a CCD camera was applied to evaluate the adhesion between the native oxide formed by conversion coating.

Keywords

Acknowledgements

The authors acknowledge the support from the Higher Education Commission of Thailand and King Mongkut’s University of Technology North Bangkok, Thailand.

Citation

Chandra-ambhorn, S., Srihirun, S. and Siripongsakul, T. (2018), "Effects of blackening parameters on the formation and adhesion of oxide on AISI 4140 steel", Anti-Corrosion Methods and Materials, Vol. 65 No. 4, pp. 383-388. https://doi.org/10.1108/ACMM-12-2017-1877

Publisher

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Emerald Publishing Limited

Copyright © 2018, Emerald Publishing Limited

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