Comparison of different agents for surface treatment of aluminium by electrochemical oxidation

Abstract

The aim of this study is to compare the corrosion resistance of anodic oxidation coatings on Al2024 alloy. Due to its composition with a high content of alloying elements (mainly Cu), anodization of this alloy is one of the difficult ones compared to most other alloys or pure aluminium. In this study, the Cr6+ free baths were used for anodic oxidation of the Al 2024 alloy because of high toxicity of Cr6+ based baths, which are legislatively restricted nowadays. One of the possible ways is the use of mixtures of organic and inorganic acids and various additives (such as e.g. tartaric, citric, glycolic, malonic acid etc.). It is also possible to use commercial products as additives for sulfuric acid anodization (SAA). In this study, the samples were anodized in four types of anodizing baths and subsequently sealed in boiling water. The surface and metallographic specimen were observed by optical microscope and scanning electron microscope (SEM). The thickness was measured using the eddy current method. The anti-corrosion properties of the layers were verified using the accelerated Machu test.