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topic 17058

Rainbow shade in anodised section (India)


It comes to my notice that some aluminium section reflects rainbow colour after anodising in sulphuric acid. Why? please suggest.

I want to Know about multicolour technology for colouring aluminium- the chemical used, working parameters, the type of bath used with metals used as cathode and anode, rectifiers, etc.Kindly suggest.

I want to know the method to calculate the anode to cathode ratio in electrocolouring bath as well as in anodising bath containing sulphuric acid - stannous sulphate(For colouring bath). Can I use lead(hollow type / flat) in anodising bath as cathode and flat type as anode? Kindly suggest.

Abhijit kumar Datta
- Kolkata, West Bengal, India

May 8, 2012

Q. Why anodized profile sometimes get burnt (rainbow colour), after electrocolouring in particular, anodising bath. Checked all cathode contacts, temp. of bath and concentration and found Okay

Ananth Nayak
Asst. Manager(Anodising) - Mysore, Karnataka, India

May 21, 2012

A. Hi,
I read your above query. I think the problem is due to oxidation occurring. Ask the operator to dip the aluminum object without giving anytime when it is out from the electropolish tank to water rinse.

Also there are special proprietary products available which can reduce your problem, when you add them in your electropolish bath.

Adhish Rathod
- Mumbai, Maharashtra, India

May 31, 2012

Q. Hi,
We do not carry out any Electropolish dip in our process. Is the burning due to any grounding of the busbars connected to the Anodising tank? Please clarify.

Ananth Nayak
- Mysore, Karnataka, India

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