Metal finishing Q&As since 1989

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Is Rit Dye Effective for Anodizing?

Current posting:

A. OK I have been using an online amperage calculator that uses the 720 rule. It is for low current anodizing. I use a 11%~12% sulfuric acid bath at room temp and I have a $60 constant current capable supply. That's important, current needs are based on total surface area front to back and voltage will vary based on cathodes, connections and other factors.

I typically run constant current at determined amperage and voltage typically is 13 to 19 volts. Battery chargers never go above about 14 and if resistance changes through the run your current density suffers.

So far I've used mostly RIT dyes and have not really come across a problematic color. But I admit that I try to achieve a 1 mil thick coating and sometimes I use a strong dye mix. I will add that no two colors are created equal. Some dyes, like for example scarlet red & especially indigo blue, come out of the bottle VERY strong and may need to be more diluted. Other RIT dyes might need higher concentrations and be heated above 45 °C. Take notes!

J Bosh
Hobbyists - INDIANAPOLIS Indiana
February 17, 2022

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⇩ Related postings, oldest first ⇩

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2001

I am doing some anodizing for a school project. I hear people referring to Rit Dye [affil links] as an effective H2SO4 anodizing dye. I have tried it and failed miserably. So far the only thing I have gotten to work is FD&C; blue #1. It sinks in well but the color is not appealing. The Rit dye (red) does not even start to penetrate, even after an hour. Setup: 12VDC 1.5amp/decimeter^2, 6061-T6 aluminum. 15%H2SO4 acid bath (by weight), approx. 30 micron thickness.

If you have actually used fabric dye and it worked please let me know how you did it.

Craig Martin
-Ithaca, New York

I've used purple RIT dye but have heard it isn't very light fast. Try using the dye warm, this worked for my red wood working dye when I started having problems and made a BIG difference. I used both dyes successfully but began having problems. I changed from 70 degree to 30 degree anodizing temperature, I guess this was why I started having problems. When I put a pc. in the dye at room temperature nothing much happened. When I warmed the dye up the pc. took on color in a few minutes.

I am using the crude method of placing a piece in and timing it. If I guessed right I repeat, if not I try again. 32 VDC amps unknown, aluminum unknown, $800+ worth of boat parts I don't have to buy. $100 worth of various scrap aluminum I turned into my own designed parts.

David Domm
- Rochester, NY USA
2001

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2007

for your anodizing set up you should find a higher amperage 12 volt charger. A minimum amperage is around 40amps. also your acid solution should about 160 degrees F. This will help speed up with your process and provide better quality. and for sealing your part after coloring just use boiling water with the part submerged for about 20 min.As for dyes good luck I am trying to find out that half myself.

Hope everything works out ok for your project
~Joe

Joe Piskac
- Lodi, Ohio