Superheater corrosion

[Itchy]

Hi I'm looking for advice on superheater problems, so first here is some of the background info.

I have a 5" Stratford J39 by Martin Evans that has recently just had a major overhaul where the boiler and superheaters were completely replaced. As for the construction of the superheaters I have followed the drawing and made the elements from stainless with the wet and hot headers made from copper. The engine has only been back on the rails since November 20010 and has not yet seen a full season's running, in this time I have only run the engine around 20 times.

I have just had to remove the superheaters to deal with the regulator as it has been leaking through. when cleaning the superheaters for reassembly I have noticed what i would consider to be some heavy corrosion at and around the solder joints at the hot header end of the assembly( the copper bit). It seems to be the silver solder that is affected rather than the copper although there is some pitting of the copper where the solder has now flaked off. In place's you can peal the dam stuff off!

I fully expect the superheaters to suffer at some point because of there environment but is normal to see this so soon. I am on my way to reassemble the engine now but will be surprised if they see the season out.

Could it be the type of Coal (Anthracite Beans), acid residue leftover from the build, or the silver solder?

[Alan Wood]

If the superheaters are working well you do get flaking on the copper hot header pipework the only idea i have is that you either did not get all the flux off after soldering or the material was not totaly clean when you soldered it.

[Itchy]

A! thank you for that Alan, that makes me feel a bit better

[Ballan Baker]

Hi, re your problem, its possible that you have not used the correct flux for stainless or as Alan says
you have not removed all the old flux, regards Ballan Baker