Title: Electrochemical studies and surface analyses of laser deposited Zn-Al-Sn coatings on AISI 1015 steel

Authors: Olawale S. Fatoba; Abimbola P.I. Popoola; Victor S. Aigbodion

Addresses: Department of Chemical, Metallurgical and Materials Engineering, Faculty of Engineering and the Built Environment, Tshwane University of Technology, P.M.B. X680, 0001, Pretoria, South Africa ' Department of Chemical, Metallurgical and Materials Engineering, Faculty of Engineering and the Built Environment, Tshwane University of Technology, P.M.B. X680, 0001, Pretoria, South Africa ' Department of Chemical, Metallurgical and Materials Engineering, Faculty of Engineering and the Built Environment, Tshwane University of Technology, P.M.B. X680, 0001, Pretoria, South Africa

Abstract: Surface hardening of mild steel with Zn-Sn bath is characterised by the traditional phases, whereas presence of aluminium leads to coatings constituted by phase in the inner layers, and by an outer layer made of three phases and inter-metallic phases which made the materials to be brittle. Enhancement in properties of Zn-Al-Sn coating led to the investigation of Zn-Al-Sn coating on mild steel by laser alloying technique. Composition of 25%Zn-50%Al-25%Sn and 30%Zn-40%Al-20%Sn with laser power of 750 W, scanning speed of 0.6 and 0.8 m/min were used in this research. Standard techniques were used for the characterisation of the laser samples and 0.5 M H₂SO₄ was used for the electrochemical test. The results showed that all the properties were improved by increasing the Al content from 40 to 50%. The optimum properties were obtained at 25%Zn-50%Al-25%Sn at laser power of 750 W and speed of 0.8 m/min. The optimum composition significantly improved the corrosion resistance of Zn-Al-Sn coatings in 0.5 M H₂SO₄ solutions and 2.2-times the hardness of the substrate was also achieved. It has been established that laser alloying of mild steel with Zn-Al-Sn coatings is promising for improving the surface hardness values and corrosion resistance.

Keywords: AISI 1015 steel; Zn-Al-Sn coating; hardness; electrochemical properties; inter-metallics.

DOI: 10.1504/IJSURFSE.2018.090054

International Journal of Surface Science and Engineering, 2018 Vol.12 No.1, pp.40 - 59

Received: 06 Jun 2017
Accepted: 18 Sep 2017
Published online: 27 Feb 2018 *

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