Surface Preparation of Aluminum Alloys for Electroplating

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IED ELECTROCHEMISTRY AND METAL CORROSION PROTECTION

Surface Preparation of Aluminum Alloys for Electroplating T. I. Devyatkinaa, S. I. Luchnevaa,*, E. N. Vasina, N. A. Cherkasheva, V. V. Isaeva, E. S. Belyaeva, and V. V. Rogozhina a Nizhny

Novgorod State Technical University n.a. R.E. Alekseev, Nizhny Novgorod, 603950 Russia *e-mail: [email protected] Received September 12, 2019; revised May 19, 2020; accepted June 30, 2020

Abstract—Various methods of surface preparation for electroplating on aluminum alloys are considered. It was shown that the most suitable of them is electrochemical anodizing. The composition and operating mode of the anodizing electrolyte were developed. The effect of the electrolyte composition on the structure and the film surface development is shown. The stability of the oxide film produced as a result of anodizing to dissolution in copper and nickel plating electrolytes was demonstrated. The relationship between the adhesion of electroplated coatings to an aluminum substrate with the relief and uniformity of oxide films was established. The proposed pretreatment is universal and can be used for any aluminum alloys in modern automatic lines without breaking the technological process chain. Keywords: aluminum alloys, oxide film, aluminium oxide, anodizing, electrochemical oxidation, chemical oxidation, copper plating, nickel plating, copper coating, nickel coating DOI: 10.1134/S1070427220090098

Aluminum and its alloys with metal coatings are widely used in many branches of technology. The range of aluminum alloys is diverse, while for each type of alloy it is necessary to select a suitable method of processing it before applying various metal coatings, the wrong choice of preparation method results in an unsatisfactory quality of the finished product, which mainly consists in the delamination of coatings from the aluminum substrate. To increase the adhesion of coatings on aluminum alloys, a number of methods for their special preparation are proposed. In world practice, zincate treatment is mainly used in existing production facilities, which requires compliance with the exact formulation of the solution for each type of aluminum alloy and the time regime [1–4]. The disadvantages of such training are described in more detail in [2, 4]. On the formed zinc surface, the next underlayer of electroplating is applied, after which a heat treatment stage is required to improve its adhesion to the substrate and to identify defective products. The need for an intermediate stage of heat treatment and the difficulties associated with the implementation of the zincate treatment process

complicate the automation of the entire technological process of deposition of multilayer coatings and its implementation on modern galvanic lines. The preliminary formation of oxide films on the surface is also utilized as a special preparation of aluminum alloys. The variety of properties of oxide films obtained by oxidation of aluminum makes it possible to use such films in solving various problems, including those requir