Does anodising change the part size?

Yes, slightly: roughly half the layer grows outward. A 20 µm layer adds about 10 µm per surface, so tight fits and threads are often masked or allowed for.

Can cast aluminium be anodised?

Yes, but high-silicon die-casting alloys give a dull grey, uneven finish. For a good look, choose a wrought alloy such as 6061 or 6063.

What is hard anodising?

A thicker anodic layer, usually 25–75 µm, made at low temperature. It is very hard and wear resistant and is used on moving or rubbing parts.

Anodising job work: types, thickness, colours and cost

Anodising is an electrochemical treatment that grows a hard oxide layer on aluminium parts. The layer protects against corrosion and wear and can be dyed in colours. Hard anodising builds a thicker, much harder layer for wearing parts.

Quick facts

For: Aluminium and its alloys (mainly)
Clear or colour anodising: About 5–25 µm layer
Hard anodising: About 25–75 µm, very wear resistant
Colours: Clear (natural), black, red, blue, gold and more
Size change: About half the layer adds to each surface
Usually priced: Per piece, per square foot or per kg

Types of anodising

Type	Layer	Used for
Clear / natural	About 5–15 µm	Corrosion protection, clean look
Colour (dyed)	About 10–25 µm	Consumer products, profiles, decorative parts
Hard anodising	About 25–75 µm	Wearing parts, pistons, valves, slides

Which alloys anodise well

6000-series (6061, 6063, 6082): very good, the most common
5000-series (5052): good
7000-series (7075): good for hard anodising, colour can vary
High-silicon casting alloys (LM6, ADC12): poor, grey and patchy finish

What to tell the anodiser

Alloy and temper
Type and thickness of anodising, and the colour
Surfaces or holes to mask (e.g. threads, fits, earthing points)
Size limits after coating for fits and threads
Quantity and how parts can be hung (rack marks)

Need anodising done?

Post your requirement free. Workshops that take your kind of work see it and get in touch. You only talk to the ones that fit.

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Related job work

Machines

VMC (vertical machining centre)

Materials

Questions

Does anodising change the part size?: Yes, slightly: roughly half the layer grows outward. A 20 µm layer adds about 10 µm per surface, so tight fits and threads are often masked or allowed for.
Can cast aluminium be anodised?: Yes, but high-silicon die-casting alloys give a dull grey, uneven finish. For a good look, choose a wrought alloy such as 6061 or 6063.
What is hard anodising?: A thicker anodic layer, usually 25–75 µm, made at low temperature. It is very hard and wear resistant and is used on moving or rubbing parts.

The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 9 October 2026.