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How to repair small surface defects prior to plating  

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What wouold be the best method to fill dents (from very small to a rather large flat) on exhaust pipes from a classic KH250 Kawasaki motorcycle prior to re-plating? I have electrolytically stripped old chrome/nickel plating down to bare metal. I am considering silver solder to fill the dents but cannot trace any references to this on the web. Does anyone out there know what would be the best method and materials to use?

I want to do all the preparation work including final polishing prior to taking the pipes to a plating shop for plating only - I have been warned that the plater should not polish after I have applied and smoothed the silver solder filling as this would cause an uneven surface finish on the softer silver solder. Are there any hints&tips to avoid this trap?

Poen Niemandt
hobbyist - Port Elizabeth, Eastern Cape, South Africa

Get them as straight as possible without any filler, even if it means doing a lot of work. Low spots can then be filled with brass brazing rod. Let the plater polish the brass down smooth before he does the plating, in fact, it would be best to let him do the repair work too. Restoration plating shops do this sort of work every day with excellent results.

If available, it may be less expensive to buy new pipes.

Jeffrey Holmes, CEF - Spartanburg, SC, USA

Thanks for the advice Jeffrey - much appreciated. The 'pipes in question has not been avaialble for many years now - I have spent about 6 months looking for a set and ended up buying a complete bike JUST for the pipes as these were the best I could find. So a new set is out of the question.

There are only one or two good electroplaters in South Africa for the sort of quality that this job requires and these guys do not offer a restoration service - they do only the plating side.

My only fear with using brass gas welding as a filler material is that the heat required for applying the filler may distort the pipe and/or make it brittle (the pipe consist of 1mm steel pressings). I have discussed the application of silver solder with (supposed) experts and it seems that it is easier to work with, requires less heat than brass brazing, and it is also easier to reshape the applied filler material.

I have already removed most of the significant dents by cutting the pipes open on the seams and tapping back the low spots - a difficult process as the sections become very floppy once the halves are split. Rewelding again was a real mission too! Most of the dents are really small and are almost invisible on the bare pipes, but chromeplating tend to magnify these imperfections 1000 times so it is imperative that the pipe surfaces are 100% flat and straight before plating.

I will look for an experienced brazing jobshop in my area and run the idea past them.

Thanks again.

Poen Niemandt
- Port Elizabeth, Eastern Cape, South Africa

You may also consider micro TIG welding for your filling part of the process. That way you may fill your parts with a parent metal (brass for brass, steel for steel, alum for alum, SS for SS, etc.). This will ease the plater's surface polishing, buffing, preparation and plating cycle.

Guillermo Marrufo
Monterrey, NL, Mexico