Surface oxidation (also called anodizing for aluminum or chemical oxidation for other metals) is an electrochemical or chemical process that forms a thin, protective oxide layer on the surface of stamped metal parts. Unlike natural oxidation (which can be uneven and porous), controlled surface oxidation creates a dense, adherent oxide film that enhances corrosion resistance, improves wear performance, and provides a base for dyeing or sealing. This process is particularly common for non-ferrous metals like aluminum, magnesium, and titanium—materials widely used in stamped parts for industries such as aerospace, electronics, automotive, and construction—due to their ability to form stable oxide layers.

For aluminum stamped parts, anodizing is the most prevalent surface oxidation method. It involves immersing the stamped part in an electrolyte solution (typically sulfuric acid, oxalic acid, or chromic acid) and applying an electric current, with the part acting as the anode. The electric current triggers a chemical reaction: the aluminum surface oxidizes to form aluminum oxide (Al₂O₃), while oxygen gas is released at the anode. The thickness of the oxide layer (ranging from 5-100 μm) is controlled by adjusting the current density (1-5 A/dm²), electrolyte temperature (15-25°C for sulfuric acid anodizing), and processing time (10-60 minutes). For example, stamped aluminum heat sinks used in electronics undergo sulfuric acid anodizing to form a 20-30 μm oxide layer—this layer is porous, allowing for the absorption of thermal compounds to improve heat dissipation, while also protecting the heat sink from corrosion in humid environments.

Anodizing offers additional benefits beyond protection: the porous oxide layer can be dyed to achieve a wide range of colors (using organic or inorganic dyes), making it ideal for decorative stamped parts like aluminum trim pieces, smartphone casings, or furniture hardware. After dyeing, the part is sealed (via boiling in water or treating with a sealing agent like nickel acetate) to close the pores, locking in the color and increasing the oxide layer’s density. Sealing also improves the part’s resistance to staining and abrasion—critical for parts exposed to frequent handling or harsh environments.

For other metals, such as magnesium or titanium, chemical oxidation (without electric current) is used. Magnesium stamped parts (e.g., lightweight aerospace components) are immersed in a solution of chromates or phosphates, forming a magnesium oxide-phosphate film that prevents corrosion. Titanium stamped parts (used in medical implants or high-temperature applications) undergo chemical oxidation in nitric acid or hydrogen peroxide, creating a titanium oxide layer that enhances biocompatibility and high-temperature stability.

Surface oxidation for stamped parts requires careful pre-treatment to ensure optimal results. The stamped part must be thoroughly cleaned to remove oils, greases, or stamping residues—typically via degreasing with solvents or alkaline cleaners, followed by 酸洗 to eliminate any existing oxide layers or surface defects. For complex stamped parts (e.g., aluminum brackets with holes or slots), special fixtures are used to ensure uniform immersion in the electrolyte, preventing uneven oxide layer formation. Post-oxidation inspections include measuring oxide layer thickness (with a eddy current gauge), testing corrosion resistance (via salt spray tests, where parts are exposed to salt fog for 24-1000 hours), and checking adhesion (using a scratch test).

Surface oxidation is a cost-effective and environmentally friendly surface treatment, as it uses non-toxic electrolytes (in modern processes) and produces a recyclable oxide layer. It also maintains the stamped part’s dimensional accuracy, as the oxide layer grows from the metal surface rather than adding external thickness. For example, stamped aluminum electrical connectors undergo anodizing to a 10 μm oxide layer—this thin film does not affect the connector’s fit in mating components but significantly improves its resistance to corrosion in electrical enclosures. Overall, surface oxidation is a versatile process that enhances the performance and appearance of stamped metal parts, making them suitable for demanding applications where reliability and durability are paramount.