Travail Pratique - Traitement de surfaces

This practical report, prepared within the Department of Metallurgy at the Université de Kolwezi, examines fundamental concepts and applications of surface treatment processes in contrast to thermal treatments for metallic materials. The first section establishes a systematic comparison between surface treatments and thermal treatments based on objectives, depth of action, modified properties, and typical applications. Surface treatments are shown to primarily alter superficial properties such as corrosion resistance, wear resistance, and aesthetics, while thermal treatments modify the internal microstructure to enhance hardness, toughness, and global mechanical performance. The report then focuses on specific surface treatment techniques. Brunishing of steel is described as a chemical process forming a thin black oxide (Fe₃O₄) layer, with analysis of its advantages, notably improved appearance and moderate corrosion resistance, as well as limitations in durability compared with galvanization and chroming. The document further contrasts electrolytic zinc coating and hot-dip galvanization, clarifying selection criteria based on thickness, surface finish, corrosion protection, and component size. Finally, a quantitative electrochemical calculation is presented for chromium electroplating of a steel sphere, determining the required current intensity using Faraday’s law, material properties, and process efficiency. Overall, the work provides a concise introduction to the theoretical principles and practical considerations guiding the choice and implementation of surface treatments in metallurgical engineering.