Effect of Nitric and Oxalic Acid Addition on Hard Anodizing of AlCu4Mg1 in Sulphuric Acid

Abstract

Abstract:The anodic oxidation process is an established means for the improvement of the wear and corrosion resistance of high-strength aluminum alloys. For high-strength aluminum-copper alloys of the 2000 series, both the current efficiency of the anodic oxidation process and the hardness of the oxide coatings are significantly reduced in comparison to unalloyed substrates. With regard to this challenge, recent investigations have indicated a beneficial effect of nitric acid addition to the commonly used sulphuric acid electrolytes both in terms of coating properties and process efficiency. The present work investigates the anodic oxidation of the AlCu 4 Mg 1 alloy in a sulphuric acid electrolyte with additions of nitric acid as well as oxalic acid as a reference in a full-factorial design of experiments (DOE). The effect of the electrolyte composition on process efficiency, coating thickness and hardness is established by using response functions. A mechanism for the participation of the nitric acid additive during the oxide formation is proposed. The statistical significance of the results is assessed by an analysis of variance (ANOVA). Eventually, scratch testing is applied in order to evaluate the failure mechanisms and the abrasion resistance of the obtained conversion coatings.

Influence of aluminium oxidation on insulation properties of oxide coating

“…Between the operations, the samples were rinsed with deionised water. Based on the literature [3][4][5][6] and the author's own experience [7,9], an electrolyte based on H 2 SO 4 and the oxidation conditions set out in Table 2 were selected.…”

“…In addition, the price of one kilogram of Al is several times lower than that of Cu. The use of Al for motor windings is also supported by the new possibility of using an electrolytic oxide coating as an insulator to separate the windings [3][4][5]. An oxide coating with a thickness of a few micrometers can replace the double plastic spacers used in copper windings with a thickness of several dozen micrometers.…”

Light-Weight Aluminum-Based Alloys—From Fundamental Science to Engineering Applications

“…Surface properties also come into play when wear and corrosion dominate a component's life span. Sieber et al [20] show that hard anodizing in sulphuric acid is an energy-efficient process that provides good abrasion resistance of conversion coatings. In ever-more complex combinations of materials in machine parts and components, the need may arise to combine AMCs with either aluminum alloys or with steel.…”

Effect of Anodic Oxidation on Tribological Behavior of 2017A Alloy

“…The anodic oxidation (Anodizing/Anodization) process is one of the methods used to improve the surface properties of aluminum alloys, such as wear resistance [1][2][3]. In the anodic oxidation process, the current is supplied to the system and the acid and water in the solution are separated into ions.…”