Bronze: discolored welds

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I've built several ornamental rails with a bronze cap, normally I would "FILE" fit all joints, so the only thing you see is a thin line. Tried something new to try an save time, so I tig welded it together, first with silicone bronze. Filed and sanded smooth, final finish was to be a "brushed" finish,( fine scotch-brite). At first it looked sweet, but the next day the weld had darkened abit. So next I cut some thin slivers directly from the "cap" for my filler and got the same effect. looks good until it starts to tarnish. I've even clear coated one, same deal I figure the heats effecting it!!!      Any ideas????????
Reply:Could you remove the original filler from the joint before the second try? I think Manganese bronze tends to give darker colored oxides than 'straight' bronze but didn't know Silicon bronze did, and don't understand why heat treating the parent metal should have that effect as long as you didn't burn out any zinc or tin while welding. I'd play with some scrap, maybe melting just a spot of the base metal and see what you can do by then annealing the surrounding area with OA  before sanding and such. Maybe try some chemical 'browning' solutions to see the difference?
Reply:All bronze will oxidize in the elements.One remedy is to treat the weldment with muratic acid. Available at hardware stores. Use gloves and rinse with water it is a strong acid. Fumes are strong,stay upwind. This will make the surface all the same color.This will make it all brand new looking.Another way is take the weldment and fine grit blast it all over, that will make it look all the same too.THE ARTISTS HANDBOOK has treatments listed for bronze.Also you can get sculptors wax at any art supply and that will protect it also.The patina of the bronze can be manipulated in many ways and produce colors,but just left outdoors it will darken just like sailboat winches etc.,.Last edited by Donald Branscom; 02-28-2009 at 01:46 PM.AWS certified welding inspectorAWS certified welder
Reply:Donald, I think he means the weld area behaves differently than the area around it so shows up after normal or induced aging.Some of the chemical treatments might help that, I think he'll just have to try some.
Reply:Pictures would make this more understandable.I'm assuming the bronze cap is discoloring.Might try brushing with staysilv silver solder flux.If it crystalizes you can wash it off with hot water.A butterfly without wings, is just an ugly bug