The authoritative public forum
  for Metal Finishing since 1989
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Sealing problem

I'm having a problem regarding my sealing (nickel free). My seal has perfect concentration, ph, and temperature. But every time I tested it with 60%-70% nitric acid by placing a drop the color was fading. I'm concerned about the long term effect of sun light on this colored anodized product.

Is it true that in time unsealed anodized aluminum develop sealing on its own?

I'm thinking somehow that the content of the color dye, may not be correct and is not correctly absorb by the pores. Can this be so? And do you think that this can affect the sealing?

Domingo Principe
- Alberta, Canada

What kind of seal are you using? You say it's nickel-free. Is a cobalt seal? These metals greater enhance the sealing properties and corrosion resistance of anodized aluminum. Have you used this seal before without a problem? What material is part made of? If its a die-casting you could have this problem even if everything is working okay.

Guy Lester
Alumin-Art Plating Co. - Ontario, California, USA