SURFACE TREATMENT OF MAGNESIUM ALLOY CASTINGS FOR CORROSION PROTECTION

• Main Authors: KUMAR ARUN M, SACHDEVA DEEPIKA, SONG GUANGLING
• Format: Patent
• Language: English
• Published: 21.06.2012
• Subjects: APPARATUS THEREFOR; CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; ELECTROFORMING; ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; METALLURGY; PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTIONOF COATINGS; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION

A method is disclosed for improving the corrosion behavior of cast magnesium alloy articles in which the magnesium alloy comprises an average composition of more than about 5 per cent by weight of aluminum. A microstructure with regions of varying aluminum content is developed during solidification. The microstructure comprises magnesium-rich grains generally surrounded by an aluminum-enriched phase on the boundaries between adjacent grains The magnesium-rich grain interiors are then selectively chemically or electrochemically attacked to leave a more corrosion resistant aluminum-enriched surface on the articles. The corrosion resistance of the articles may be further enhanced by one or more of anodizing, aluminizing or painting the corrosion-resistant aluminum-enriched surface.