44064

Electroless nickel plating peel off and corrosion problem / Pin holes in Aluminum surface [India] 

February 17, 2007

Dear All ,

we manufacturing parts using Exctrusion Aluminium Alloy - 2014A - h15 grade / T6 WP condition material. After getting the machined aluminium housing , we do electroless nickel plating on this aluminium part . This is has to withstand very hard & tough environmental conditions ( -40 deg to +150 deg C , Hot & cold temperature cycling ) .
The problem I face is 2 types ,
1. we observe pin holes and porosity on the machined part of surface of aluminium housing
2. Due to this the electroless nickel plating is getting peeled off during various test conducted to test the finished aluminium housing.

3. Even this plating is getting corroded during salt spray test conducted for very long duration .

what would have been the problem which we face now???

pls give your suggestions.

Thanks,

T.S.Sivakumar
Electronics manufacturing - India

Presuming that typical processes were performed between machining and EN plating, possibilities include:
Dull tooling or improper cutting fluids.
Inadequate cleaning.
Over-etching.
Inadequate desmutting.
Poor zincating (thin, double zincate is preferred).
Poor strike coating (alkaline EN?).
Inadequate EN filtration.
Inadequate EN agitation.
Excessive byproducts in EN bath.
Inadequate additives (stabilizers, anti-pitting, etc.) in EN bath.
Inadequate rinsing between any steps; DI water is necessary before the 2 EN solutions.

For pretreatment, zincating and a neutral electrolytic nickel strike (if so desired), see ASTM B253 [link is to spec at TechStreet], 'Standard Guide for Preparation of Aluminum Alloys for Electroplating.' Also, many metal finishing books are available: http://www.finishing.com/Books/index.html

If using 'homebrew' EN solution, this is often 'penny wise and pound foolish.' Proprietary solutions produce quality coatings over a longer bath life and come with professional advice.

Ken Vlach - Goleta, California

All of what Ken said is very true. But, the best plater in the world can not overcome cheap metal that the housing is made out of. There should be absolutely no visible pits after machining.

James Watts
- FL