Sulphuric Anodising

Sulphuric anodising is an electrolytic finishing treatment for aluminium, offering excellent protection and corrosion resistance.

Precision Coating Thickness
Wide Material Compatibility
Industry-Standard Compliance

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Sulphuric anodising creates a clear finish that enhances durability and extends the part's functionality.

The process creates a thin layer of aluminium oxide, with its thickness controlled and measured using XRF equipment. While it serves various purposes, sulphuric anodising is commonly used for decorative finishes that also require some corrosion resistance. Sulphuric acid anodising, also known as soft anodising, typically produces a coating between 5–25 µm. For enhanced corrosion resistance, a thickness closer to the upper end of this range is recommended. In addition to clear anodising, we offer a variety of colour options, including black. The final colour can be influenced by the material's grade and composition, with a minimum coating thickness of 15 µm generally applied.

Material Suitability

We anodise aluminium, specialising in 6000/7000 grades. Material composition impacts results; consult datasheets or contact us for suitability.

Coating Thickness

Sulphuric acid anodising creates coatings of 5–25 µm; thicker layers, over 15 µm, improve corrosion resistance and colouring.

Anodising Standards

We follow BS ISO 7599 anodising standards and can meet additional specific requirements based on our customers’ needs.

Surface Conditioning

We offer a variety of surface conditioning processes:

Masking: We precisely mask areas not requiring anodising, even on intricate details.
Vapour Blasting: Vapour blasting uses air, water, and abrasive media for a smooth finish, without altering part dimensions.
Pre-treatment / Etching: Etching removes contaminants, preparing parts for anodising.

Jigs

To maintain consistent electrical contact during anodising, parts must be securely held in jigs. We offer a range of jigs and can create custom solutions if needed. To avoid visible marks on decorative surfaces, additional features may be required in the design. Please specify jigging requirements on the part’s drawing for optimal results.

Maximum size criteria

Milturn’s new 2,500 sqm facility offers the capacity to process both small and large components, with batch sizes ranging from one to thousands. Equipped with large anodising tanks and a heavy-duty crane, we can anodise components up to 3m x 1m x 1m in size. Contact us today to discuss your specific requirements.

Sulphuric Anodising FAQ's

Explore our FAQs to find answers to common inquiries. If you need more information, our team is here to help, please don’t hesitate to get in touch.

The material composition must be checked to ensure suitability for anodising. Some grades may anodise, but the finish quality can vary. Anodising is generally unsuitable for alloys with over 4% copper or more than 7% silicon. Additionally, sharp edges should have a radius to avoid issues, and blind holes often receive a thinner coating.

Material grade also affects the final colour. While we have over 20 years of experience with coloured dyes, exact colour matching between batches cannot always be guaranteed. However, achieving consistent results is typically possible.

We can perform sulphuric acid anodising on castings; however, the finish quality is typically lower than that of non-casted parts. Please contact us to discuss your specific requirements.