Sulphuric acid anodising is a common electromechanical process which is used on aluminium surfaces to create a protective layer. The process thickens the natural oxide of the aluminium, leaving a hard yet porous and adherent layer before sealing.
How does it work?
Aluminium pieces are placed in an acid bath, where it becomes the anode. Current is then passed through the electrolyte, causing oxygen to form on the surface. This then builds an oxide which is uniform and with fine pores. Technicians adjust acid strength, temperature and current density to balance porosity with the take-up of dye and hardness against speed.
Technicians have to comply with organisational policy and procedures for the sulphuric acid anodising activities undertaken and report any problems that they cannot personally resolve, or are outside their permitted authority.
Before the process begins, the parts are degreased, then lightly etched before being rinsed. There are many expert sulphuric acid anodising companies which carry out this work, such as www.poeton.co.uk/surface-treatments/anodising/sulphuric-acid-anodising.
At the end of the process, the parts are sealed in nickel acetate or hot water to close the pores and lock the finish.
Why is it used?
Sulphuric acid anodising gives excellent corrosion resistance, even in harsh environments, and is also resistant to wear, because it increases surface hardness. This means it is less prone to scratches and abrasions. As the finish is transparent, it can be dyed in any colour, because the oxide layer is porous. It is typically used in everyday products like fixtures, valves, optical and camera instruments and aerospace hardware.
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