Small Scale Aluminium Anodising in the Home Workshop

Summary

In this video, the creator shares their personal experience with anodising aluminum, emphasizing that it's not a tutorial but rather a recounting of their process. Over three years, they've learned the importance of preparation, safety, and using the right chemicals, such as sodium hydroxide and sulfuric acid. They cover key steps like cleaning, etching, anodising, dyeing, and sealing, highlighting trial-and-error moments with different dyes. Despite some challenges, they achieve a successful result for a part of a puller they're working on, with tips for DIY enthusiasts in the UK.

Takeaways

• 😀 Anodising requires a clean, smooth surface as it doesn't hide imperfections, so start with a well-prepared part.
• 😀 Safety is crucial when working with chemicals like sodium hydroxide and sulphuric acid—always wear gloves, eye protection, and old clothes.
• 😀 When mixing chemicals, always add the chemical to the water, not the other way around, to prevent dangerous reactions.
• 😀 In the UK, obtaining sulphuric acid for anodising can be tricky, but drain cleaners with 91% acid can work as a substitute.
• 😀 Etching the aluminium in a 2% sodium hydroxide solution cleans the part but may dull polished finishes.
• 😀 A constant current power supply is ideal for anodising, as it ensures consistent results, with the current set according to the part's surface area.
• 😀 The cathodes in anodising should be made of a conductive material like aluminium foil, but lead is often preferred for better results.
• 😀 Thorough cleaning of the part is essential—use brake cleaner and MEK to ensure no grease or oil remains before anodising.
• 😀 The anodising process involves submerging the part in a sulphuric acid bath for around two hours while monitoring the current.
• 😀 Dyeing the anodised part is optional, but using proper anodising dye yields better, more permanent results compared to fabric dyes.
• 😀 After anodising, the part must be sealed by simmering it in boiling water for 40 minutes to improve corrosion resistance.

Q & A

What is the main goal of this anodising guide?

The main goal of the guide is to share the author's personal experience with anodising small parts, providing insight into the process from a UK perspective. It’s not meant to be a professional 'how-to,' but rather a 'what I did' account, including what worked and what didn’t.

What precautions should be taken when working with anodising chemicals?

Precautions include wearing gloves, eye protection, and old clothes, as anodising chemicals like sodium hydroxide and sulphuric acid can be dangerous. Always add the chemical to water, not the other way around, and ensure you have a tidy workspace to avoid accidents.

What is the purpose of using sodium hydroxide in the anodising process?

Sodium hydroxide is used to clean the aluminium before anodising. It creates an etching solution that removes grease, dirt, and oxidation from the metal, providing a clean surface for the anodising process.

Why is distilled water preferred over tap water in the anodising process?

Distilled water is preferred because it has fewer impurities, which helps prevent unwanted reactions during the anodising process. Tap water can contain minerals or contaminants that may affect the outcome of the anodising or dyeing.

What type of acid is used in the anodising solution, and how is it prepared?

The anodising solution is made with 91% sulphuric acid, which is diluted with distilled water to create a 15% acid concentration. The acid should be added gradually to the water to avoid a dangerous exothermic reaction.

What type of power supply is used for anodising small parts, and why is it important?

A power supply that can provide a constant current is ideal for anodising small parts. The author uses a 5A 24V power supply but recommends a constant current supply for better results, as it ensures a consistent current throughout the anodising process.

How is the aluminium part connected to the power supply during anodising?

The aluminium part is connected to the positive terminal of the power supply using soft uncoated aluminium craft wire. Multiple connections are made to ensure the part stays securely attached, as the anodising process will cause the oxide layer to form and potentially break the electrical contact.

Why is a homemade magnetic stirrer used in the anodising process?

The magnetic stirrer is used to prevent bubbles from sticking to the surface of the aluminium part during anodising. This helps ensure a more uniform and effective anodising process.

What is the purpose of the sodium hydroxide etch bath, and how long does the part stay in it?

The sodium hydroxide etch bath is used to clean and prepare the aluminium part by removing any grease, dirt, or oxidation. The part is typically left in the bath for about 20 seconds before being rinsed in clean water.

How is the dyeing process carried out, and what type of dye is used for anodised aluminium?

After anodising, the part is rinsed and then submerged in anodising dye. The author uses a proper anodising dye, which gives deeper, more vibrant colors compared to fabric dyes. The part is agitated in the dye until the desired color is achieved.