How aluminum anodizing works, coating thickness choices, masking strategy and dimensional impact on machined parts.
Anodizing is the default surface finish for aluminum CNC parts - but Type II vs Type III, clear vs black, and masking choices all affect performance and price.
Type II vs Type III
Type II (decorative) builds a 5-25μm layer, ideal for appearance and moderate corrosion resistance. Type III (hard anodizing) builds 25-100μm for wear resistance - common on drone parts and hydraulic components.
Color and Masking
Clear, black, and custom colors are dyed into the porous oxide layer. Bearing bores and threaded holes usually need masking - specify masked surfaces upfront to avoid rework.
Dimensional Impact
Anodizing grows the part dimensionally: roughly half the coating thickness is added to each surface. For tight bores, tell your supplier the post-coating tolerance you need.