Hard anodized black, also known as Type III or hardcoat anodizing, produces a much thicker oxide layer, typically ranging from 25 to 75 micrometers (0.001 to 0.003 inches), compared to soft anodized black (Type II), which is generally thinner, between 5 and 30 micrometers. This increased thickness contributes to superior wear resistance, with hard anodized surfaces demonstrating up to 100 times better wear resistance than untreated aluminum. The hardness of hard anodized black is typically around 60–70 on the Rockwell C scale, comparable to case-hardened steel, whereas soft anodized finishes are harder than bare aluminum but significantly less so than hard anodized coatings.
