How is the black processing of aluminum parts done?

Process black active treatment, controlled chemical oxidation coloring, generating protective film

• Five-step coating process

1. Pretreatment: Cleaning → degreasing → oxide layer removal → activation, achieving "thorough oil removal, uniform alkali etching, and clean water washing".
2. Blackening reaction: immersed in room temperature blackening agent, 15 ~ 30℃ reaction for tens of seconds to a few minutes, the formation of black alumina film. Also can choose high temperature route (135 ~ 155℃ alkaline solution).
3. Cleaning and cooling: Rinse thoroughly to remove tank residue.
4. Closed treatment: soak anti-rust oil or varnish to lock the pores of the film.
5. Quality inspection: check the uniformity of the film and whether there are cracks falling off.

• How to repair if the blackening has already occurred?

1. Light: oil removal cleaning + fine throw + closed can be restored.
2. Medium: nitric acid light + water washing + re-passivation.
3. Severe: there are pits and erosion, can only be sandblasted and redone surface treatment.