303 ISSN 0027-1314, Moscow University Chemistry Bulletin, 2018, Vol. 73, No. 6, pp. 303–306. © Allerton Press, Inc., 2018. Original Russian Text © E.V. Pometun, V.I. Tishkov, A.A. Pometun, 2018, published in Vestnik Moskovskogo Universiteta, Seriya 2: Khimiya, 2018, No. 6, pp. 445–449. Practical Aspects of Pretreatment of Aluminum Surfaces for Industrial Anodizing E. V. Pometun a, b, *, V. I. Tishkov c, d, e , and A. A. Pometun c, d a Sechenov First Moscow State Medical University, Moscow, Russia b Alufinish, Moscow, Russia c Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, Russia d Innovations and High Technologies MSU, Moscow, Russia e Department of Chemistry, Moscow State University, Moscow, 119991 Russia *e-mail: epometun@gmail.com Received January 12, 2018 Abstract⎯The most widely adopted techniques for etching aluminum surfaces for industrial anodizing are described. The processes involved in the dissolution of surface layers of aluminum in acidic and alkaline media are described in terms of their economic and ecological viability and practical use. The advantages of using composite alkaline etching solutions are demonstrated. Keywords: anodizing, electrochemical anodization, aluminum etching, surface treatment, galvanic produc- tion, treatment of galvanic production waste waters, industrial safety DOI: 10.3103/S002713141806007X Surface oxidizing treatment can be defined as a process in which an oxide film on the surface of a part is created due to a redox reaction, and is used to impart protective, protective-decorative, or electrically insu- lating properties to the part’s surface [1]. Surface oxi- dizing treatment is used for different materials and pieces that can be metallic (alloys) or nonmetallic (e.g., silicon) [2, 3]. By convention, surface oxidizing treatment, depending on the particular way of creating a coating, is classified as thermal, plasma, or electro- chemical oxidation. Surface finishing of aluminum alloys is typically carried out in electrolyte solutions by passing electrical current. Because the part being treated is connected as the anode in an electrolytic cell, this process is known in the literature as electro- chemical anodization or anodizing [4]. Anodized parts are used in various areas of science and technol- ogy. The larger part of the production of the anodizing industry is made up of aluminum alloy profiles des- tined for use in building construction and interior design, with the decorative properties of these prod- ucts being particularly important. Apart from the anodizing stage, the technology of industrial anodizing includes a number of stages con- sisting in the chemical and mechanical treatment of the surface (both pre- and post-treatment), and wash- ing parts with water between the stages. The properties and surface structure of the Al 2 O 3 surface film depend primarily on the technological stages the part was sub- jected to before the film was formed [5]. For instance, the surface roughness (Ra) of parts intended for anod- izing must conform to the requirements [6] that pre- scribe Ra < 10 μm for protective coatings and <1.6 μm for protective-decorative coatings. Under typical ambient conditions, the Al–air interface is known to be mediated by a thin (up to 3–5 μm) layer of amor- phous Al 2 O 3 . To create a structured artificial layer of this oxide, the natural oxide layer is stripped at one of the pretreatment stages by partially dissolving away a thin surface layer (etching). With the known ampho- teric behavior of aluminum, both acidic and alkaline baths with different compositions were developed. The physicochemical properties of etching baths have a strong impact on the texture and optical characteris- tics of the target product. The proof of the validity of the different treatment procedures is a topic of debate, and we addressed this question in specialized publica- tions [7]. Here, we discuss different mechanisms of aluminum dissolution in acidic and alkaline media used in industrial etching processes. ALKALINE ETCHING Currently, many plants and factories (including Russia) whose primary activity is aluminum anodiza- tion tend to comply with the international standards for the galvanic industry and voluntarily apply for quality certification. The Zurich-based Qualanod One is the most authoritative independent interna- tional association for quality control in the anodizing