Sulphuric Acid anodising


Anodising – Sulphuric Acid Anodising

Sulphuric acid anodising is typically 10 – 15µm thick. It is used for its anti-corrosion properties, when additional durability is required or when colouring by dying is required. Sulphuric anodising leaves a clear silver coloured finish but we are able to offer a range of colour dyes giving the part a superior visual finish.

Anodising takes place at the metal interface, so that the oxide grows out of the surface, converted from the metal. Since the oxide has twice the volume of its parent metal, the coating grows 50% out from the original surface and 50% into the original surface. In consequence, the increase in the size of the anodised part is half that of the coating thickness, a factor to be taken into account when considering size tolerance.

As the coating grows, the electrolyte and electrical current must continue to gain access to the oxide metal interface, producing more oxide. Since aluminium oxide is an insulator, this could be a problem, but the coating structure forms a matrix of porous (sub-micron size) columns, from the surface to the interface, and oxide conversion continues at the base of the columns. As the coating thickness builds, and the electrical conductivity to the interface decreases, the rate of coating growth falls exponentially, so that the process cannot continue indefinitely.

Poeton offer sulphuric acid anodising to all major Aerospace and Military specifications.

For advanced anodising solutions see Apticote 300.

Materials Processed:

Aluminium Alloys

Tank sizes: Gloucester

2m x 1m x 1m

Tank sizes: Cardiff

3m x 1m x 1m

Tank sizes: Poland

1.2m x 1m x 1.2m

The tank sizes shown above are approximate sizes only. If you have a larger part then please contact us as we may still be able to help.


Electrical icon

Electrical Insulation

Corrosion icon - acid spilling on to rectangle

Good Corrosion protection (350hrs salt spray)

Blue paint brush icon

For colour dying, yielding deep rich colours.

A lock icon on a shield for toughness

Preferred over Chromic anodising when the coating needs toughness, scratch resistance and durability.


Rail braking systems

Landing gear components


Electrical component casing

Military vision systems, with black dye

Sulphuric Acid anodising