Formation of Anticorrosive Film for Suppressing Pitting Corrosion on Al-Mg-Si Alloy by Steam Coating

Ai Serizawa,Tetsuya Yokomizo,Kotaro Mori,Kohei Watanabe,Takahiro Ishizaki,Takuhiro Oda

doi:10.3390/coatings8010023

Abstract

Al alloys offer excellent physical and mechanical properties, such as a low density, high specific strength, and good ductility. However, their low corrosion resistance has restricted their application in corrosive environments. There is a need, therefore, for a novel coating technology that is capable of improving the corrosion resistance of Al alloys. In the present study, we examined a steam-based method of forming a corrosion-resistant film on Al alloys. Al-Mg-Si alloy was used as the substrate. The cleaned substrates were set in an autoclave with ultrapure water as the steam source and processed using different temperatures and holding times, resulting in the formation of anticorrosive films on the alloy. FE-SEM images of the film surfaces showed that plate-like nanocrystals were densely formed over the entire surface. XRD patterns indicated that the film was composed mainly of AlOOH crystals. The potentiodynamic polarization curves revealed that the corrosion current density of the film-coated substrates significantly decreased, and that the pitting corrosion was completely suppressed, indicating that the corrosion resistance of the Al-Mg-Si alloy was improved by the film formed by means of steam coating.

Highlights

Given the lightness of Al, Al alloys are frequently used as structural materials
The objective of the present study is to develop a new coating technology that is environmentally friendly, and contributes to the creation of a sustainable society
Evaluation of Corrosion Resistance steam‐coatedfilm film on Al-Mg-Si the Al‐Mg‐Si alloy was characterized from the viewpoints of

Summary

Introduction

The superior mechanical and physical properties of these alloys make them ideal for use as structural materials. These properties include a high strength-to-weight ratio, good formability, high thermal conductivity, and excellent recyclability. Given these properties, Al alloys have found numerous applications in a wide range of industries, including automobiles, building, and heat-transfer components. Al-Mg-Si alloys are lightweight medium-strength heat-treatable Al alloys with an excellent combination of cost-effective engineering properties that makes them ideal for a wide range of applications, from the transportation [7,8] and building industries [9] to high-voltage power transmission [10] One series of Al alloys, namely, Al-Mg-Si alloy (AA6000 series aluminum alloy), has been utilized to fabricate lightweight automobile body panels due to its good precipitation-hardening response at the temperature that was used to cure the paint applied to the vehicle (approximately 170–180 ◦ C) [1,2,3,4,5,6].

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Results

Conclusion