Galvanic Corrosion

[Bob Butts]

Hi Guys

I am building the late Tiger tank and wondering whether to paint it.

The question I have is will, for example, the brass parts on the wheels suffer from galvanic corrosion even though an electrolyte is not present.

If so, how do people build these unpainted models.

Many thanks

Bob

[Adrian Harris]

This is an extreme example as the inside of the tank was not primed or painted, and was then left outside for several months.

I always prime where disparate metals will be in contact, as moisture will always wick in between any gaps it can find.

These pics show what happened to the outside, which was not primed but was painted.

2009-08-05_12-12-11.jpg (160.93 KiB) Viewed 2793 times

You can clearly see where the water has sat between the two metals.

Adrian.

[Bob Butts]

Good grief - is it normal to leave them outside in the rain?

My tank doesn't fight in the rain!

[Bob Butts]

Good grief - is it normal to leave them outside in the rain?

My tank doesn't fight in the rain!

[Jerry Carducci]

Some of my other models are aluminium with steel, brass and copper parts attached and after 40+ years they've not had
any noticeable issues with galvanic corrosion and I never paint the inside. For my Lee I did (mostly) paint the inside
of the upper hull but not the lower and used different primers for steel vs aluminium parts. I don't plan on changing my
policy of not painting the inside of lowers. Perhaps if I was in a very humid area. I am on the West coast here but not near enough
to the ocean for it to figure in. When I did live near the ocean many years ago I did definitely see the results of galvanic corrosion of aluminium
/steel and aluminium/brass parts first hand but they were in fog and moisture constantly yet even after nearly 10 years the corrosion did not threaten mechanical integrity. And again I'm sure there are conditions where it would do but it should be easy to avoid these.

My reasons for not painting the insides of models has its origins in that I began this hobby with gas/glow powered models
and the combination of fuel residue, oil and paint always resulted in a gooey sticky mess and the first exposure to that
was enough.

I never run my models through rain or standing water/mud if I can help it. If I really want to I still maintain a fleet of 1/16 scale models for that....
but never my 1/10 or 1/6 models...

Jerry

[Adrian Harris]

> Good grief - is it normal to leave them outside in the rain?

It was the original Sherman prototype. The previous owners of Armortek put it on their proving ground outside the Dunkeswell factory as a range wreck.

To my knowledge it spent at least nine months sitting there, probably longer.

Hopefully this year I'll get it running again.

Adrian.

[Bob Butts]

OK - I understand - Great restoration project and good luck with it.

[Bob Butts]

Thanks a bundle Jerry.

[GlenStenhouse]

The many different metals / alloys will form the electrolysis process. Lump of zinc in the hull to give up sacrificial electrons can help. If leaving unpainted then a coating of clear lacquer will protect it. otherwise there are products like soft seal but these are a thin film that rubs off and that needs reapplying every now and again so not ideal.