Contact usPenta Precision offers hard anodising through our trusted network of subcontractors, available exclusively for components we machine in-house.
At Penta Precision, we make hard anodising available as part of our complete machining service.
By working with a trusted network of approved finishing specialists, we ensure your components are delivered with the protection and performance you need, without adding extra steps to your supply chain.
Many of our customers choose us after experiencing delays or quality problems elsewhere, valuing the reliability and consistency we bring to every project.
Hard anodising (Type III sulphuric acid anodising) is a specialised electrochemical treatment applied to aluminium to produce a much thicker, harder oxide layer than standard (Type II) anodising. The process uses a more concentrated sulphuric acid electrolyte, low temperatures (often close to 0 °C), and higher voltage or current densities to grow the oxide film.
The anodised oxide is not a surface coating, but a conversion of the aluminium substrate itself — it becomes metallurgically bonded. The resulting layer is dense, though still porous, which gives both increased wear resistance and electrical insulation.
Typical thicknesses for hard anodised layers are in the range of 25-60 µm, depending on the alloy, required wear resistance, and sealing method. Thinner layers within this range may be used where dyeing or cosmetic appearance is required, since heavy thickness tends to darken the natural finish.
The process usually concludes with sealing to close the oxide’s pores. Hot de-ionised water is commonly used, and sometimes chemical sealing additives — such as nickel acetate or other agents — may be employed to enhance corrosion resistance.
Hard Anodising gives best results on 6061 or 6082 aluminium alloys but any 6000 or 7000 series aluminium is generally suitable for hard anodising. 1000, 2000 and 5000 series can be hard anodised but with some compromises. Please call our team to discuss.
Anodising is somewhat of an "artisan" practice rather than a precision process. As such, although there are defined controlled processes that a compotent processor will run, there are certain factors that will effect results and may be out of their control.
For example, colour matching can be very difficult when it comes to hard anodising. Some factors can be controlled such as layer thickness and the conditions at which the anodising are done. However, there are some factors beyond the control of the anodising engineer such as thermal history.
Among the various types of anodising processes, two prominent methods stand out: Hard Anodising and Sulphuric Acid Anodising. In this blog, we delve into the distinctions of each of these finishing processes, comparing their benefits, common applications, and suitability for CNC machined components.
