Alkaline corrosion properties of laser-clad aluminum/titanium coatings

Abstract

Purpose

The purpose of this paper is to study the use of titanium as a protecting element for aluminum in alkaline conditions.

Design/methodology/approach

Aluminum coatings containing up to 20 weight per cent Ti6Al4V were produced using laser cladding and were investigated using light optical microscope, scanning electron microscope – energy-dispersive X-ray spectroscopy and X-Ray Diffraction, together with alkaline exposure tests and potentiodynamic measurements at pH 13.5.

Findings

Cladding resulted in a heterogeneous solidification microstructure containing an aluminum matrix with supersaturated titanium (<1 weight per cent), Al₃Ti intermetallics and large partially undissolved Ti6Al4V particles. Heat treatment lowered the titanium concentration in the aluminum matrix, changed the shape of the Al₃Ti precipitates and increased the degree of dissolution of the Ti6Al4V particles. Corrosion testing showed significant localized dissolution of the aluminum matrix.

Research limitations/implications

Increased titanium concentration and heat treatment gave improved alkaline corrosion properties. At pH 13.5, the Al₃Ti phases were protected, while the aluminum matrix corroded.

Practical implications

For alkaline corrosion-protection of aluminum in the automobile industry, titanium might be useful at pH values below 13.5 or by using other coating techniques.

Originality/value

This is the first study testing the use of titanium as a protective element of aluminum in stringent alkaline conditions.

Citation

Aggerbeck, M., Herbreteau, A., Rombouts, M., Verwimp, J. and Ambat, R. (2015), "Alkaline corrosion properties of laser-clad aluminum/titanium coatings", Anti-Corrosion Methods and Materials, Vol. 62 No. 1, pp. 37-47. https://doi.org/10.1108/ACMM-07-2013-1290