Anodizing Cost: Type II, Type III and Area
Anodizing is an electrochemical conversion of the aluminium surface rather than a coating applied on top of it, and that distinction explains its cost structure. There is no powder to spray and no film to cure; the cost is area, current, time in the tank, and how efficiently parts can be racked.
Anodizing is priced by surface area, the number of parts per rack, the process type, the coating thickness and sealing step, plus masking and colour work. Type III hard anodizing costs materially more than Type II because it runs longer at higher current and consumes more rack time.
Why anodizing is priced by area and rack time
The oxide layer grows from the substrate, driven by current through the electrolyte. Current scales with the total surface area of every part on the rack, and time in the tank scales with the thickness required. So the price follows area and thickness together, not part count.
Racking is the part buyers do not see. Every part needs an electrical contact, and contacts leave an unanodised mark that has to sit somewhere the customer will not notice. Parts that rack densely are cheaper per piece; long, thin or awkward parts that need individual fixtures are not.
Type II and Type III are different products
| Type II (sulphuric) | Type III (hard anodize) | |
|---|---|---|
| Typical thickness | 5–25 µm | 25–50 µm and above |
| Hardness | Moderate surface hardness | Substantially harder, more wear-resistant |
| Appearance | Clear or dyed, decorative options available | Typically darker, less colour latitude |
| Relative cost | Lower — shorter cycle, standard electrolyte | Higher — longer cycle, tighter process control |
| Best for | Appearance, corrosion resistance, dyeing | Wear surfaces, sliding contact, abrasive duty |
| Design note | Part growth is small but must be allowed for | Growth can affect fits; allow for it on tight bores |
Type II versus Type III anodizing
Thickness, sealing and what they add
Thicker coatings take longer in the tank, so cost rises with the specification rather than staying flat. Unsealed anodizing is porous and will absorb dye or contamination; sealing closes the pores and is normally part of a specified finish rather than an optional extra. Where a customer asks for a thickness without stating whether it is sealed, we ask, because it changes both durability and price.
The other thickness consequence is dimensional. The oxide grows outward from the original surface — roughly half into the metal and half out — so a 25 µm coating moves a surface by about 12 µm per side. On a cosmetic panel that is irrelevant. On a press-fit bore or a mating shoulder it is the difference between fitting and not fitting.
Colour, masking and minimum charges
Clear anodizing is the baseline. Dyed colours add a batch step and a colour-matching risk, because the alloy and temper affect how deeply the dye takes — the same dye on 5052 and 6061 will not give an identical result, and no anodizer can promise an exact match across alloys. That is a property of the process, not a limitation of a particular shop.
Masking costs follow the same logic as in coating: threads, bores and electrical contact points have to be protected or machined after the fact. And because the process is a tank cycle, there is a minimum charge — a rack has to be filled and run, and small batches share that minimum rather than dividing it.
What to put on the drawing
- Process type and thickness — Type II or Type III, with the thickness range.
- Whether the finish is to be sealed.
- Colour to a standard where a dye is required, accepting that alloy-to-alloy matching has a tolerance.
- Masking instructions for threads, bores, mating faces and electrical contact areas.
- Where dimensional allowance is needed, and the critical dimensions that must survive the coating.
Frequently asked questions
Is anodizing cheaper than powder coating?
For simple clear anodizing on aluminium it can be comparable; for dyed or hard anodizing it is usually more expensive than powder coating the same area. The comparison only becomes meaningful once both options are specified on the same part with the same durability requirement.
Why is Type III hard anodize so much more expensive?
Because it runs longer at higher current density with tighter temperature control, and thicker coatings consume more tank time per part. The rack also carries fewer parts per cycle at the thicknesses involved. You pay for process time, not for material.
Will anodizing change my part dimensions?
Yes, by roughly half the coating thickness per side, because the oxide grows out of the substrate. On a 25 µm coating that is about 12 µm per surface. Allow for it on fits and bores, or mask the feature and specify the tolerance so we can hold it.
Can you match a specific colour exactly?
To a reference standard over a defined alloy and temper, normally yes. Across different alloys, no — the same dye bath produces a different shade on 5052 and 6061, which is a property of the process. If colour consistency across mixed alloys matters, tell us at enquiry and we will discuss the options.
Do you anodize in-house?
Anodizing is coordinated with specialist finishing partners rather than run under our own roof, because the process needs its own certification structure and effluent handling. We control the specification, the inspection and the delivery, and we say plainly which operations are partner-executed.
Send the drawing, get a real answer
An engineer reviews your model for manufacturability and returns a costed quotation — with the DFM observations that would change the price.