The process described below is a not hard anodizing but decorative.
Anodizing aluminium is easy but the simplest way doesn't work with all the aluminium alloys. You will have bad results with 2017 and 2024 (dural) excepted with very dark colors. It works well with the 5xxx, 6xxx and 7xxx series.
The steps are :
1- degreasing the aluminium parts
2- Anodizing.
For this operation you need a non conductive tank (pyrex is well) and a power source about 15 V (a 12V car battery is fine, it's a 13,8 V one !); the solution in the tank is 80% distilled water and 20% sulfuric acide. Connect the anode (+) to the aluminium part and the cathode (-) to a large sheet of lead (with gloves please !); The density of the current will be a bout 1A to 2A dm2. You can use a variable resistor for the regulation or some car light bubbles. Let in the bath for 30-40 mn. After that you will rince the part with water and a basic solution (ammoniac, soda ash, Deskstop ...)
3 - Coloring
The most findable coloring agent in France is used for clothes under the brand name DYLON. It's a powder you add to boiling water. Immediatly after anodizing put the aluminium part in the colored boiling water during 2 or 3 minutes. Dry it and repeat until you find the best coloration.
We have opened the alumine cells by anodizing, colored them and we must closed the cells. There is different solutions.
- Hot water just before boiling (<100° C)
- Nickel and Cobalt acetate (not easy to find !)
- Sodium silicate
- Salts of toxic metals !
- Linseed oil (or any fat)
Hot water (close alumine by hydration) and linseed oil are the simplest. I have tried the two ways and find that I get better results and durability with the second one.
You can see some drawings of the tank, regulator ... on my wapics site (this is not for anodizing but copper electro-plating and electro-formingbut it's the same principe
WAPICS - TRAITEMENTS ELECTROCHIMIQUES )
Hope that is helpfull !
Aerobscure
WAPICS - TABLE DES MATIERES DU SITE "cnc - fonderie - outillage - moteurs LRK "
aerobscure "les pionniers de l'aviation avant 1914"