Hard Anodizing (Type III)

Hard Anodizing (Hard‑coat Anodizing / Type‑III), sulfuric acid low‑temperature process; oxide film thickness 30‑50 μm per side, coating continuous, uniform, no powdering, no peeling; surface hardness HV ≥350, providing wear resistance, corrosion resistance, and electrical insulation properties; the coating grows approximately 50% inward and 50% outward, resulting in a dimensional increase of about 20‑25 μm per side on the part—precision mating areas require pre‑machining allowances; sharp edges must be chamfered with R≥0.5 to reduce burning and cracking at edges; the natural color is gray to dark gray—if black hard anodizing is required, an additional dyeing step is needed; die‑cast aluminum is not suitable for this process.