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Tin plate Blistering


Q. Hello out there

We are having problems on a tin electroplated breather tube which is soldered to a terne coat fuel tank.

The tube is steel with a copper flash deposit followed by a tin plate of 15 microns. When soldering, using oxyacetylene and solder wire, the plating adjacent to where the solder is applied blisters into bubbles of tin depleting the surrounding areas. The final result looks like sweat drips.

Previous parts used a thinner coating of tin which did not experience this problem.

Is the blistering a function of coating thickness?
Is it caused by dissolved gas or porosity?
Would it be beneficial to drop the copper flash?

Thanks in advance for all replies.

Graham Dodd

A. Hi Graham, I tried to answer a very similar question on thread 49424, only to learn from Mike Berrier a lot more than I taught :-)
The first thing to determine, as you will see on that thread, is whether you are seeing blisters or you are actually seeing blobs because the causes are different. If it's blobs, it's most likely an excess of brighteners/organics in the tin plating ... and it makes sense to me that thicker plating will probably involve more organics based both on just more of it with thicker plating, and the fact that more organics may be required or perceived to be required to get smooth bright plate when it's thicker. Good luck!


Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey

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