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Chem Film Does Not Appear to Coat Holes Made After Plating.

I am having trouble chem filming holes in a machined aluminum part that has been gold plated. The holes are tapped after plating and show no evidence of chem film application after 5 minutes in process. I will detail specific operations below. Let me know if you have any theories as to why this will not work, or suggestions to make this work. Thank You

Material is 6061 Aluminum-plated as follows--Electroless nickel per MIL-C-26074 [on DLA], Class 3, grade B, .0002 thick, then Gold plated per MIL-G-45204, Type III, Grade A, .000005 thick. Holes are tapped following the above process and then Chem filmed per MIL-C-5541E with Chemetall Oakite-Chromacoat 103.

D. Bohnet
- Yankton, South Dakota USA
2001

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Perhaps there is a residue in the hole from the tapping operation. Do you use a lubricant for tapping? How is that cleaned out?

Larry Hanke
Minneapolis, Minnesota
2001

When aluminium is plated with gold it reaches to its holes as acc to low current density theory and some of them are filled with nickel before gold process

Sharad
- Faridabad State, India
2003