01How the process works
Parts are etched and anodized as the anode in an acid bath, growing a porous oxide that can be dyed and is then sealed to close the pores. Hard anodizing produces thick wear resistant layers at low temperature.
Oxide thickness, seal quality, colour match and surface defects such as etch marks or burning are the checks. Hard anodizing grows partly outward, so dimensional allowances must be considered on machined parts.
- Pretreatment. Degrease, etch, desmut.
- Anodizing. Oxide grown in acid bath.
- Colouring. Dye or electrolytic colouring.
- Sealing. Hot water or cold seal.
- Testing. Thickness, seal, colour.
02What typically goes wrong
| Defect | Typical cause | How it is found |
|---|---|---|
| Low oxide thickness | Current, time | Eddy current gauge |
| Poor sealing | Seal bath condition | Dye spot or admittance test |
| Colour variation | Alloy, bath, time | Colour measurement against samples |
| Burning | Poor contact, high current | Visual |
| Etch marks and streaks | Pretreatment | Visual |
| Dimensional growth | Hard anodizing | Measurement |
03Where an inspector should look
01
Before production
- Class and thickness
- Colour limit samples
- Masking
02
During production
- Bath temperature and current
- Seal bath control
03
After production
- Thickness
- Seal test
- Visual and colour
04Standards and references
ISO 7599 (anodizing of aluminium), ISO 10074 (hard anodizing), Qualanod specifications for architectural anodizing.
Standards are named for orientation. The applicable edition and acceptance criteria are those in your contract and specification.
05How we support buyers of anodizing parts
Coating, Painting and Galvanizing InspectionSurface preparation, paint application, DFT, adhesion and hot-dip galvanizing inspection against the coating specification.
Independent Quality ControlIncoming, in-process and final quality control performed independently at the supplier, with measured results and clear acceptance decisions.