Aluminium smokeboxes

[BazParticipant @baz89810]

Gentlemen,

The loco I am currently building has an aluminium casting for the smokebox. Over the Christmas holidays I have machined the smokebox and bored it out to a snug fit to the copper boiler. When telling a couple of club members about my progress I was told that I would need a special sealant for ally to copper, something to do with electrolytic action, they could not tell me what the stuff is but think that it is used on Winson locos as some of these have ally smokeboxes and also on the Pollys. Are there any builders out there who have these locos and have been told the same as me, or what did you seal the smokebox to boiler with?

[BazParticipant @baz89810]

[Jeff DaymanParticipant @jeffdayman43397]

You probably don’t want to hear this, but aluminum in contact with steel or copper will result in some galvanic corrosion, especially when wet and or in contact with acidic ash. I would suggest aluminum smokeboxes in general are a real bad idea, but that’s just my opinion.

 

For longevity I suggest a copper, brass, bronze or stainless smokebox, or well-primed and painted steel, will give much longer lasting results and no corrosion-bubbled paint. I would roll a new box in one of these materials rather than use an aluminum one, again just my opinion.

 

If you must use an aluminum ‘box, I would say that if both parts are smeared with a film of  silicone sealer wherever they touch, separated and allowed to dry, then on final assy more silicone is used to fill the gaps, this will provide a good galvanic barrier. High temp silicone as used for auto engines will work OK.

 

No silicone based sealer is paintable however, and anything the silicone touches will be extremely hard to clean to prep for paint.

 

JD

 

PS you may have a heck of a time getting paint to stick to alum as well, unless you use an etching primer as used on aircraft.

Edited By Jeff Dayman on 03/01/2011 15:49:53

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