The Study on the Overall Plasma Electrolytic Oxidation for 6061–7075 Dissimilar Aluminum Alloy Welded Parts Based on the Dielectric Breakdown Theory

Abstract

Electrical connection of dissimilar metals will lead to galvanic corrosion. Therefore, overall surface treatment is necessary for the protection of dissimilar metal welded parts. However, serious unbalanced reactions may occur during overall surface treatment, which makes it difficult to prepare integral coating. In this paper, an overall ceramic coating was fabricated by plasma electrolytic oxidation to wrap the 6061–7075 welded part integrally. Moreover, the growth mechanism of the coating on different areas of the welded part was studied based on the dielectric breakdown theory. The reaction sequence of each area during the treatment was verified through specially designed dielectric breakdown tests. The results showed that the high impedance overall of ceramic coating can inhibit the galvanic corrosion of the 6061–7075 welded part effectively.

Corrosion of the Welded Aluminium Alloy in 0.5 M NaCl Solution. Part 2: Coating Protection

“…Jiang et al formed thick epoxy coatings (~100 ± 10 μm) on AA2024 aluminium alloy [2,3]. Among the methods of protective coating formation on the surface of Al alloys, one of the most promising methods is plasma electrolytic oxidation [5,6,7,8,9,10,11,12,13,14,15]. Serdechnova et al grew layered double hydroxides on PEO-pretreated AA2024 Al alloy [6].…”

“…Egorkin et al formed protective coatings on 5754 Al alloy with high mechanical and protective properties using PEO in a mixed electrolyte with microsecond polarizing current pulses [14]. Chen et al showed that PEO can effectively inhibit dissimilar aluminium alloy welded parts against galvanic corrosion [15]. The properties of the formed surface layers depend on the polarization mode of PEO, electrolyte composition, and chemical composition and structure of the treated alloy [16,17,18,19,20,21].…”

Surface Modification of 6xxx Series Aluminum Alloys

“…They noted that PEO coating has improved hardness and corrosion resistance. Chen et al [58] used PEO as a process tool to protect the weldment involving dissimilar materials combination of 6061 and 7075 Al alloys. They noted that the PEO oxide coverage on the weldment has different morphology and composition compared to PEO coating on the substrate materials.…”

Влияние Структурной Гетерогенности На Коррозионное Поведение Алюминиевых Сплавов И Их Сварных Соединений

“…Например, формируются толстые эпоксидные покрытия (~100 ± 10 мкм) на алюминиевом сплаве AA2024 [824,825]. Для создания защитных покрытий на алюминиевых сплавах активно используется плазменное электролитическое оксидирование [49,81,86,88,145,543,544,552,[827][828][829][830][831][832]. Получены ПЭО-слои на алюминиевых композитах в силикатно-щелочном электролите при переменнотоковом режиме оксидирования [831].…”

“…На поверхности алюминиевого сплава 5754 методом ПЭО были созданы защитные покрытия с высокими механическими и защитными свойствами в электролите смешанного состава с использованием поляризующих импульсов тока микросекундной длительности [552]. Показано, что методом ПЭО можно эффективно снижать гальваническую коррозию на поверхности сварных деталей из различных алюминиевых сплавов [827]. Исследованы зависимости свойств сформированных покрытий от режима ПЭО, состава электролита, состава и структуры обрабатываемого алюминиевого сплава [284,[833][834][835][836][837].…”