BLACK ANODIZING TOUCH UP SOLUTIONS

[LONDONDERRY]

Okay I have a question. We have a part that is black anodized and need some machinging rework, which I did. Because of the rework the black anozing was removed during machining. Additionally, the part is 6061 aluminum with a stainless steel PEM stud pressed in. My questions are:

Is it possible to reanodize this part with the PEM inserted, or does it have to be removed or can it be masked over?

If we choice not to reanodize this part, can it be touched up by another means, besides using a black sharpie pen? It there such a thing as an black anodize touch up pen?

Thanks
Frank

 

[alexit]

Your anodize vendor can try to redip the part but appearance is not so good, usually vendor will want to strip and re-anodize whole which will change part dimensions 0.05-0.2mm. Not handheld touchup I know of...

They should be able to mask the PEM, solution probably has little effect on PEM but will cause bleed and poor appearance on anodize if not done. We usualy put PEM in after anodize but still mask hole to permit conductivity and prevent anodize from changing hole size.

We use semi-gloss black enamel paint like for children's airplane as touch up, can also mix with small bit of water to make finish more grey when dry and have rougher surface to match anodize.

 

[LONDONDERRY]

Birchwood Casey BPP Super Black Touch-Up Pen

How about this product every use it?


Thanks
Frank

 

[kenvlach]

LONDONDERRY,
1) Brush anodizing is possible. Dyeing and sealing are additional steps which would be done conventionally (immersion).

2) Touch-up anodizing parts w/o stripping is possible -- the parts must be sealed and any inserts well masked -- other metals will draw all the anodizing current and burn up. Also, stop at a lower voltage than used in the initial anodizing.

3) Touch-up using chemfilm is permitted for anodize per MIL-A-8625F: up to 5% of surface area using chemfilm per MIL-C-5541 (then use a black sharpie on the chemfilm. Just dip in deox & DI rinse before chemfilm. SS inserts are OK (don't need masking) for chemfilm.

4) Touch-up pens per MIL-A-8625F. The only approved chemfilm pen (Form D on QPL-81706) is the Alodine 1132 Touch-N-Prep Pen from Henkel. Easy to use: just deox. the scratch using a Q-tip wetted with 20-50 vol% nitric acid, rinse with DI water and apply. QPL:

http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=95728

Henkel's website for Alodine conversion coatings shows both a Brush Alodine® 120 Kit and the Touch-N-Prep® Pen:

http://www.aerospace.henkel.com/index.cfm?ID=170

I don't see the Birchwood-Casey pen mentioned; their ALUMA BLACK® A14 BRUSH-ON is rather expensive (but it does produce a black coating w/o dyeing):

http://www.birchwoodcasey.com/store/antiquing.html