I remember an old post here, from Polisher, talking about fixing pits in diecast pieces before rechroming. IIRC, he said they carved out the pits like a Dentist would, then used Silver Solder, to fill the pits. Metal finish, polish, then Chrome. Sounds simple. Everyone knows we can't weld diecast parts, to steel. But has anyone ever tried using Silver Solder to join diecast to steel ?
I don't recall the specific post, but there was one here where the builder soldered a pair of die-cast headlight rings to fenders, then either leaded or bondoed to blend it all together. I would assume you'd want to remove the chrome to bond to the base metal.
My 1st Q to look up, would be the melting point of Silver Solder, since I don't remember. Even 35% takes some heat - like from an Ox/Ac torch. At least when I had to do it for some specific A/C repairs at past-work, on buses. 2nd Q would be melting point of diecast, since I don't know. Don't think that's all that high, & I think there're different kinds - so that'll make a difference, but afaik, it's above ~400*F where the "aluminum solder-sticks" melt at. This will be interesting. Marcus...
After a quick search: The jewelry people have a variety of Silver Solder alloys, with melting temps ranging from 1207 F to 1490 F. Encouraging. Pot Metal, doesn't have a specific alloy, but it is mostly Zinc. The melting temp for Zinc is around 800-850 F. Hmmmmm. Doesn't sound right. The original story might not have been completely accurate.
Thanks for the replies. Starting to think I remembered it wrong. More research: turns out the coefficient of expansion for Zinc, how much it moves when it gets hot, is 3x that of Mild Steel. Of course, body parts shouldn't get that hot.
The way it is done in an electroplating shop is to remove the existing chrome, then clean and prep the part for plating. First run through would be a copper 'strike' (Rochelle process) in the alkaline bath to cover everything with a thin layer of copper and to protect the underlying metals from the next step. Next the part is plated in acid copper bath to lay on the heavy copper that will be worked out by the polisher to smooth out the pits. Once the polisher has removed what they can, hopefully without cutting through to the base metal, it is cleaned and additional copper is plated in the acid bath. A little is plated if moving on to nickel/chrome afterward or a lot if the polisher needs to work out more pits in the part. If the polisher cuts through to base metal the part has to be run through the copper strike before going back to acid copper. Basically the copper is the bondo in this process. Then you get into taking care not to change the part dimensions too much, lose detail and the like. There's lots to plating, especially the high end plating.
Once it’s copper plated you can soft solder pits etc and file it up, then back into copper, then buff taking lots of care as the buffing could melt the solder (translation? The stuff made of tin and lead?)
Soul-derr, sol-da, sodder, or soda, depending on what part of the world it's in As an aside, love the avatar. My young son got a ride in Moore's Missile around the back streets of Merrylands, back when John Brown owned it. Took a good month to get the grin off his face Cheers, Harv
Harv I had the chance in the late '70s to buy Harrop's Howler. It was in the old Trading Post for sale at Windsor but I was living in the caravan park at Berowra heights at the time so had no where to work on it. I think it was for sale for $1500. Wished I'd bought it and stored it back in Newcastle at my parent's place.
I've soldered steel to steel lots of times when welding would not suffice. They sell a very small butane torch at Harbor Freight and other places called a "micro-torch". I also use a specific liquid flux from Harris. The trick is not to apply too much heat or the stuff turns black and you have to clean it off and try again. I simply play the micro torch over the parts and try to heat them evenly and test every so often to see if the solder melts when touched to the parts. Then apply the solder and a little more heat as needed. Obviously get a scrap part to try it on first. I don't know if its still cool enough for pot metal because I never tried that, but it seems as though the pot metal should take more heat than the solder.
Now that would have been cool. Ron Harrop's story is another one that really deserves a book. Sorry for the thread hijack Unkl Ian... two Aussies caught up in 50's-era drag sedans Cheersm Harv
Brownells gunsmith ing supplies sells a low temp high strength solder https://www.brownells.com/tools-cle.../adhesives-solder/hi-temp-hi-force-44-solder/ Dan
Some pot metal trim will melt with a propane torch. Got to watch the melting point. I tried a few different heat sources to see if I could fill some pits. All I did was distort some of the die cast vents.
I used a product called MuggyWeld for modifying my grille bar. I painted mine after bodyworking with all metal filler. The Muggy Weld is a multi-alloy rod and you use their flux. Heat until the flux turns brown (no more) and it works great. practice on some crap first and FOLLOW THE DIRECTIONS. Not sure about use for chroming, check with chromer first. I removed the outer spears and narrowed 1-1/4" to the inside of each turn signal.
BITD the preferred solder for filling pits in pot metal was Certanium 34C, but it seems to be unavailable stateside although I think you can still get it in the UK. It was suggested to drill out the pitting, solder with a low flame (I think it melted around 450*), finish to suit and hand it over to the plater do his magic.
I am of no help. At work people would bring pot metal stuff in for repair; meaning for me to weld [heli-arc] back together. I would try different alum looking rods or strips cut from what ever looked right. Either I got it healed or turned the item into a glob, 50/50.
The Jalopy Journal
