Hard anodising converts aluminium surfaces into a dense, wear-resistant oxide grown from the base metal. Run at low temperatures and high current, it yields thicker layers than decorative anodising and improves life in abrasive conditions. Because part of the film grows inward and part outward, dimensional allowance keeps tolerances tight. Colour is dark grey or black unless a specific finish is required.
How Hard Anodising Works
Parts are cleaned, etched and racked for electrical contact, then processed as the anode in chilled sulphuric electrolyte while current builds a controlled oxide. Parameters such as alloy, bath temperature, agitation and current density steer thickness, hardness and porosity. Sealing in hot water or nickel acetate closes pores where corrosion resistance matters. Leaving layers unsealed can help paints or dry film lubricants key to the surface when adhesion is a priority.
To learn more about hard anodising, reach out to an expert such as https://www.poeton.co.uk/surface-treatments/anodising/hard-anodising/.
Benefits, Uses and Standards
Thicker oxides lift hardness, reduce galling and resist wear on sliding parts, yet heat dissipation remains good because the layer is integral to the aluminium. Typical uses include valve bodies, pistons, guides, tooling, camera housings and cycle components.
Specifying and Aftercare
When specifying, state alloy, target thickness, tolerance class, masking, any areas to remain clear and whether sealing is required. Note that high-copper alloys may discolour and castings can vary. Ask for sample coupons and certification for thickness and seal quality.
Clean parts with mild detergent, avoid abrasives, and protect contact faces during assembly. With sound specification, hard anodising gives durable performance at a sensible cost.
