Thread: Soldering Galvanized Steel for Powder Coat

We are a custom lighting and metalwork manufacturer. We solder galvanized steel all of the time and are quite comfortable working with it.



However, occasionally we have a need to powder coat our fixtures, but with the oven temp (~400F) at about the same as the melting point of our typical 50/50 solder, we usually have to rivet instead.


We know that silver solder has a much higher melting point and that's been recommended, but we're not sure whether easy, med, hard is most appropriate and/or if there's something else that's better for steel.


Any thoughts or guidance? Thanks

Any of the silver solders at almost any blend should do fine on steel to steel bonds, i commonly use the 40 - 50% silver because it wicks very well but its expensive. Anything above 10% should be just fine.

Im not familliar with the easy medium hard concept? But ymmv

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Originally Posted by caskwarrior

Im not familliar with the easy medium hard concept? But ymmv

Thanks for the quick reply! We're not familiar with it either, but pretty common I guess for jewelry. Seems like Easy would be fine since still well above oven temps. This source doesn't show composition...

Easy medium hard refers to the silver content. Easy has a high silver content (wicks and flows easily) hard is at the lower end of the scale.

How are you soldering the parts? If you’re using a copperhead iron you will have to get proficient with a small torch to use silver solder, a copperhead won’t transfer sufficient heat.
2% or 5% will be more than adequate to fix your parts, and is substantially cheaper but needs a bit more skill with the torch. It’s not difficult but a couple of rods worth of practice joints will go a long way. You’ll also need to make sure you scrub the flux off properly, if you don’t it eventually blisters the powder coat off the finished part.

As you’re powder coating give some consideration to using cold rolled sheet instead of galvanised, soldering with a torch burns the galv off, and powder coat generally requires the parts to be blasted prior, so it’s kind of a pointless coating.

Thanks for the splainer! We use 250 watt American Beauty irons with iron clad tips, so should be good there. I'm assuming you mean 2% or 5% silver content, so we'll look for that.

Totally get the redundancy/belt & suspenders on powder coating galvanized, but it's cheap enough and we keep it in stock. And, for (2) fixtures, it's not worth getting CR steel sheet.

silver solder will require temps that will destroy the galvanizing....okay on bare steel but not galvanized sheet unless you happy with the fact that the galvanizing will burn away....and dont breathe those fumes in

The extra heat may also cause distortion problems.?

i wouldnt use 2-5% silver...to much heat required and the low silver silver content makes it a pain in the backside on steel. if you go down the track of brazing then 45% silver (ie blue tip in Australia) would be the go.
If you must go for a lower silver content then a minimum of 15% may be okay...but you will experience problems with it taking to steel (bare) as compared to 45%..... 45% will be better but even then it does take some practice to get it right (unless you have prior experience)

Not worried about galvanizing but am worried about warping. Not sure I can find a lead free solder with melting point 500 - 600F...

For two fittings, you might be better looking at alternate finishes, and maybe have them sprayed with some 2 pack paint.

Originally Posted by racingtadpole

For two fittings, you might be better looking at alternate finishes, and maybe have them sprayed with some 2 pack paint.

We do a very durable vinyl resin and offer that as an alternative to powder coat, but some clients are hell bent on PC, despite the added cost, etc.

Just had a browse through your website.
Some really nice work in your gallery pictures

Maybe something like this would be suitable https://www.cigweld.com.au/product/9...ck-15g-coil-1/ I have used this this for many years on radiators hot water service etc, can be use with irons, I sure there would be a equivalent product in you neck of the woods.

Originally Posted by racingtadpole

Just had a browse through your website.
Some really nice work in your gallery pictures

Well, thank you very much! You obviously have good taste!

Originally Posted by China

https://www.cigweld.com.au/product/9...ck-15g-coil-1/ ... equivalent product in you neck of the woods.

Thanks for the tip. Couldn't find any specs on it, like composition or melting point. At this point, we would probably go with 10/90 Sn/Pb, which has a melting point in the low 500sF, so not likely to warp. Really don't want my guys to use lead solder, so unless this client rejects the rivets, we'll give up this pursuit of solder for powder coating. Just hard to accept that this isn't a more common issue...

Thanks everyone!

965- melting point app. 221c (429F) Sn (Tin) 96.5%, Ag (Silver) 3.5%,Tensile strength 60MPaDensity7.5g/cm3, Soldering Iron temp 281c (537F)

Originally Posted by China

965- melting point app. 221c (429F)

Thanks, but that's too close to powder coating oven temp.