Hand machined mechanical pencils

Aluminium anodising (27/07/11)

There is plenty information out there on the web about home anodising, so I'm not going to go into detail. I was mainly concerned about getting a deep black colour and I found the following procedure worked for me.

  1. Clean part with hot water and detergent
  2. Dip in conc. sodium hydroxide solution until surface fizzes and turns a uniform greyish colour
  3. Rinse in water
  4. Anodise for 45 minutes at a current density of 15mA/cm2 in a 20% sulphuric acid solution with a lead cathode. Voltages are typically 10-20V, depending on part size. Hold part using aluminium wire.
  5. Rinse in water
  6. Soak for 20 minutes in dye solution at 50°C. Dye is Sanodal Deep Black MLW (http://www.gaterosplating.co.uk/Anodising-Dyes.php) at a concentration of 10 grams per litre.
  7. Rinse in water
  8. Boil in clean water for 45 minutes to seal anodising layer
  9. Dry and buff up with a clean cloth

The dye I have is about 30 years old but still seems to work fine. Here are some pictures of a small part (18mm square) anodised with the above procedure.