Promoted Anodizing Reaction and Enhanced Coating Performance of Al-11Si Alloy: The Role of an Equal-Channel-Angular-Pressed Substrate.

Zhou Zhou,Ma Ma,Wu Wu,Jiang Jiang,Qiao Qiao,Song Song,Gao Gao,Sun Sun,Liang Liang

doi:10.3390/ma12193255

Abstract

In this paper, the effect of the equal-channel-angular-pressed (ECAPed) substrate on the coating formation and anticorrosion performance of the anodized Al–11Si alloy was systematically investigated. The ECAP process dramatically refines both Al and Si phases of the alloy. The parallel anodizing circuit is designed to enable a comparative study of anodizing process between the cast and the ECAPed alloys by tracking their respective anodizing current quota. The optimum coatings of both alloys were obtained after anodization for 30 min. The ECAPed alloy attained a thicker, more compact, and more uniform coating. Energetic crystal defects in the fine Al grains of the ECAPed substrate promote the anodizing reaction and lead to the thicker coating. Fragmented and uniformly distributed fine Si particles in the ECAPed alloy effectively suppress the coating cracks, enhancing the compactness of the coating. Overall, the ECAP-coated sample exhibits the best anticorrosion performance, which is evidenced by the concurrently enhanced prevention of coating and improved corrosion resistance of the substrate.

Highlights

Aluminum (Al) and its alloys are widely used lightweight structural materials, which have low density, high specific strength, excellent thermal conductivity, and great availability [1]
In enhanced protection from the anodizing coating and the improved corrosion resistance of the substrate can be be protection from the anodizing coating and the improved corrosion resistance of the substrate can argued to elucidate the significantly improved anticorrosion performance of the argued to elucidate the significantly improved anticorrosion performance of the equal-channel angular pressing (ECAP)-coated sample at aa microscopic microscopic level
The significantly refined microstructure of the Al–11Si alloy was achieved via multi-pass ECAP process

Summary

Introduction

Aluminum (Al) and its alloys are widely used lightweight structural materials, which have low density, high specific strength, excellent thermal conductivity, and great availability [1]. Al alloys have good corrosion resistance in less aggressive environments, owing to the efficient protection of its amorphous passive oxide film [2,3]. In humid environments and acidic or alkaline solutions, they still suffer severe corrosion damage [4]. Cl− , accelerate the corrosion damage of Al alloys by forming soluble salts such as AlCl3 on the surface of metals, replacing the original hydroxide thin films. The integrity and stability of the hydroxide passive films in solutions are vital to the corrosion resistance of Al alloys [5]. An effective approach to increase the corrosion resistance of Al alloys is to fabricate coating layers on the surface to create barriers against direct

Results

Discussion

Conclusion