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Zincate doesn't stick to aluminum bus bar from some suppliers

Q. Hello
Just a quick question in relation to an issue we have been having lately. We are tinning on aluminum substrate for busbar production. We have noticed that with certain types of bar we see our zincate (first dip) not adhere to the substrate completely and we are wondering what can be done to possible resolve this issue

Our current setup
Alkaline Degreaser bath followed by two rinses
Alkaline Pickling followed two rinses
Acid Desmutting bath followed by two rinses
Electroless Zincate (first application) x2 rinses
Acid Zinc strip then x2 rinses
Second hit of zincate then x2 rinses
Nickel Strike x2 rinses
Acid Tin followed by acid rinse
Hot air dryer.

Since this we have got SEM testing on all types of bar, this is only issue with one certain supplier the rest plates perfect. The billets show nothing different in the composition of the bar itself. What I have noticed is that the roughness sq is <0.2 on the problem bar and >0.4 on bar with no issues to plate on.
Can you advise how much affect this would have in overall tin plating

Thanks Ryan

Ryan McGrory
- Donegal Ireland
December 8, 2020

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December 10, 2020

Q. Hello,

The nickel strike is an intermediate layer between the zincate and acid tin, this is to help with over tin adhesion and surface preparation of the aluminium bar, this also stops any zinc migration to affect our bright tin finish.
The first zincate layer is taken off in the zinc strip and then goes into the zincate for a second time to provide a fine uniform finish.

The issue we're having is adhesion of the first and second zincate to the aluminum substrate; on a certain supplier the zincate can be seen as a poor coverage and also flaking off into the subsequent rinses

If the zincate plating isn't correct at this stage we are going to have problem with adhesion in nickel strike and acid tin.

We have looked at our pretreatment steps and carried out lab scale testing to bring these to optimum level but no success.

Possibly the aluminium need to be treated before going through our plating line but again unsure on what step to do so

Thanks Ryan

Ryan McGrory [returning]
- Donegal Ireland

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