Experimental Studies on Corrosion Behavior of Ceramic Surface Coating using Different Deposition Techniques on 6082-T6 Aluminum Alloy

Abstract

Aluminum alloys cannot be used in aggressive corrosion environments application. In this paper, three different surface coating technologies were used to coat the 6082-T6 aluminum alloy to increase the corrosion resistance, namely Plasma Electrolytic Oxidation (PEO), Plasma Spray Ceramic (PSC) and Hard Anodizing (HA). The cross-sectional microstructure analysis revealed that HA coating was less uniform compared to other coatings. PEO coating was well adhered to the substrate despite the thinnest layer among all three coatings, while the PSC coating has an additional loose layer between the coat and the substrate. X-ray diffraction (XRD) analysis revealed crystalline alumina phases in PEO and PSC coatings while no phase was detected in HA other than an aluminum element. A series of electrochemistry experiments were used to evaluate the corrosion performances of these three types of coatings. Generally, all three-coated aluminum showed better corrosion performances. PEO coating has no charge transfer under all Inductive Coupled Plasma (ICP) tests, while small amounts of Al3+ were released for both HA and PSC coatings at 80 °C. The PEO coating showed the lowest corrosion current density followed by HA and then PSC coatings. The impedance resistance decreased as the immersion time increased, which indicated that this is due to the degradation and deterioration of the protective coatings. The results indicate that the PEO coating can offer the most effective protection to the aluminum substrate as it has the highest enhancement factor under electrochemistry tests compared to the other two coatings.

Anodizing of AA6082-T5 by conventional and innovative treatments: Microstructural characterization and dry sliding behaviour

“…PEO is an electrochemical conversion treatment, based on the modification of the growing anodic oxide by micro-discharges, initiated at potentials above the breakdown voltage [4], sometimes also termed Micro-Arc Oxidation (MAO). Several comparative studies have been published on PEO and HA [5][6][7][8] and the main advantages of PEO over HA can be summarised as follows: (i) use of dilute alkaline electrolytic baths instead of concentrated acidic solutions; (ii) higher thickness, hardness, practical adhesion and wear resistance of PEO layers, with possible incorporation of anions from the bath; (iii) higher tolerance towards alloying elements such as Cu and Si than the conventional hard anodizing process. All these features are related to specific PEO treatment conditions, derived from conventional anodizing but involving higher voltages (above dielectric breakdown of the anodic oxide) so as to generate micro-arc discharges which assist and enhance the growth of oxide-based layers.…”

Preparation and Performance Optimization of Original Aluminum Ash Coating Based on Plasma Spraying

“…Commonly used spray powders range in price from a few, to a few hundred dollars per kilogram. Among them, high-purity alumina powder is one of the commonly used spray powders, the main component of aluminum ash is alumina, and the price is low [27][28][29][30][31]. If we can replace the high-purity alumina coating with aluminum ash coating, this will not only reduce production costs, turning waste into treasure, but also protect the ecological environment.In this study, a method for the utilization of waste aluminum ash was proposed.…”

Fatigue Resistance of an Anodized and Hardanodized 6082 Aluminum Alloy Depending on the Coating Thickness in the High Cycle Regime

“…[ 1 ] To enhance the tribological and corrosive properties for meeting the requirements of the respective application anodizing is a classical approach. [ 2,3 ] By this electrochemical surface treatment, the aluminum substrate is converted to alumina producing strong adherent coatings with cellular‐arranged pores without influencing the microstructure of the substrate. [ 4,5 ]…”