Letter 35089

Green anodizing of titanium sword [New York] 

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I have been trying to acquire some titanium (which is remarkably hard to buy) to create a katana to anodize green (it just seems like a interesting thing, I'm in 9th grade (15 yo) with my parents permission), but i can't seem to find the right voltage, my friend let me try his but all i got was dark blue sort of stuff.

Nathan Figueroa
Student - NY, NY, USA

In USA you can buy small quantity of titanium from Reactive metals studio. They sell anodizing equipment and booklet too. Good luck!

Goran Budija
- Zagreb,Croatia

To get a green colour on titanium is hard - it is the last colour you get with anodising as you raise the voltage before the oxide layer goes grey, and with some alloys you don't get a green at all. It usually takes about 70-90 volts DC, which can give you a nasty shock, so wear rubber gloves and avoid anything that could cause a short circuit. However, if you are fully aware of the safety precautions, then try it, with adult help. You need to make the titanium the anode and use a piece of stainless steel as the cathode. For the electrolyte I use dilute sodium or ammonium sulphate or phosphate solution. I estimate that a strength of about 1 gram per 100 ml would be enough. If it is too concentrated, a large current will flow and you can get sparking as you lower the sword into the electrolyte - quite dramatic, but not good for the oxide colours ! The best way to get the colour you want is to gradually increase the voltage while taking the metal out to check it. Sometimes each colour takes a couple of minutes to develop. The sequence of colours from 5 volts up is brown, purple, dark blue (20 V), light blue, yellow (40 V), gold, pink (50 V), magenta (pinky purple), emerald green (70 V), apple green, grey. Good luck !

Jeremy Wyatt
- Epsom, Surrey, England

Ed. note: To emphasize Mr. Wyatt's cautions, this sounds like a good idea for a science project that can be done under the supervision of your science teacher. Not all adults (in fact few adults) are trained in safely working with electricity, and these voltages are definitely not innocuous.

i want the rato of mixing acid and the voltage to be applied .i am using sulphuric acid for colouring of titanium ahd lead sheet as anode .so please tell me what i have to do for bringing green colour in titanium

h.arivazhagan
- puduvai,tamilnadu,india

Hi, H. Mr. Wyatt has already told us what voltage to apply and that he uses dilute sodium or ammonium sulphate or phosphate solution as the electrolyte. I think the answer to your question then is to use dilute sodium or ammonium sulphate or phosphate solution at the voltage he suggests, rather than to ask what voltage to use for sulphuric acid :-)

Good luck.

Ted Mooney, P.E.  finishing.com Brick, NJ

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