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Negative results on Iridite touchup

Hello,

In an attempt to "touch-up" an aluminum surface with an Iridite conversion coating, the Iridite color has turned dark green/dark blue. What, exactly, has happened?

We have made several attempts to thoroughly clean the surface with an etch and water rinse, but with NO deoxidizer the surface color has gone dark when Iridite is applied.

Has the oxide of aluminum converted to an aluminum chromate salt which is green in appearance? Is the surface protected even though the surface is green?

Your opinions please.

Chris Friedberg
- Newington, Virginia, USA
2004

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2004

I don't recall ever seeing a dark geen/blue color when Iridite is used for touch up. The proper procedure is to clean the area using a solution of about 10-15% phosphoric acid to which a small amount of wetting agent is added. Using Iridite 14-2 at 4 oz/gallon, wipe or brush on the damaged area for about 1-3 minutes depending on how dark you want the yellow color. You may be using another Iridite perhaps one designed for zinc or Cadmium. Be sure to use Iridite 14-2. There are brush-on Kits available from Macdermid

Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
           and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])

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2004

Don,

Very much appreciate the info.

The DUPONT aluminum conversion coating #226S STEP B will be shelved.(An Alodine reg. coating chemical)

The dissolution phosphoric acid is available through FISCHER SCIENTIFIC Distributors or equivalent metal treatment warehouse.

Chris Friedberg
- Newington, Virginia

We have seen this happen recently to Alum 7075. After following our in-house procedure we noticed both green and dark staining. It was removed using scotch bright but never figured out what caused it. Has anyone found out what the cause is. please respond

S.Parry
- Chatsworth, California
November 5, 2008