Under-Water Superoleophobicity of Heat Treated and Chemically Etched Hypoeutectic Aluminum- 8 wt.% Silicon Alloy

Nyong Aniedi E,Awaka-Ama Joachim J,Ubuo Emmanuel E,Ite Aniefiok E,Nsi Edet W,Rohatgi Pradeep K

doi:10.35840/2631-5076/9236

Abstract

Hypoeutectic aluminum-silicon alloy consisting of 8.0 wt.% silicon and prepared through a solid-phase technique was studied for the contact angle behaviour of oil in under-water condition. The surface structure of the Al-8 wt.% Si hypoeutectic alloy was modified through a solutionizing heat treatment process at 650 ℃ for 6 hours, quenching in water and etching in Keller's reagent. The modified surface structure showed an increase with the etch time for sizes of the secondary arm-spacing (SAS), from 5.31 ± 2.54 μm to 6.16 ± 2.35 μm for 5 to 20 seconds of etching respectively. Equally, while the average surface roughness (R<sub>a</sub>) increased from 0.1 to 0.74 microns, the sizes of the secondary dendrites (SSD) reduced considerably with increase in the etch time. These alterations of the surface structure influenced the fractional surface area (f<sub>so</sub>) and the evaluated contact angles of oil drops at the solid-water interface. Therefore, a gradual increase in the contact angles of oil, to a maximum value of 159.96 ± 0.64, was noted for the Al-8 wt.% Si alloys after the solutionizing heat treatment, quenching and etching process, confirming significant under-water superoleophobicity.

Highlights

Aluminum and its alloys have enormous applications in the automotive, electrical as well as in the aerospace industries [1,2]
We explore a simple, new and effective method of the creating under-water superoleophobic surfaces on a hypoeutectic aluminum-silicon alloy at the solid-water interface through a regime of heat treatment, quenching in water regime and chemical etching
The alloy was allowed to cool in an inert atmosphere, created by argon gas and the ingots obtained thereof were weighed and cut into smaller sizes for surface treatment through grinding and polishing, heat treatment and chemical etching with Keller solution

Summary

Introduction

Aluminum and its alloys have enormous applications in the automotive, electrical as well as in the aerospace industries [1,2]. The surfaces of aluminum and its alloys are often exposed to reactive liquids and oils in various situations, which can induce surface tarnishing, corrosion and fouling thereby reducing their time-span of usefulness. To this end, there has been considerable interest recently in the development of under-water superoleophobic surfaces on aluminum and its alloys for various reasons some of which are for self-cleaning, anti-smudge, anti-fouling and anti-corrosion applications [3,4].

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Conclusion