Author Topic: Powder coating and Soft Solder...  (Read 305 times)

Online Kim

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Powder coating and Soft Solder...
« on: January 02, 2021, 05:45:20 AM »
I'm currently struggling with sliver-soldering a fairly sizable hunk of steel.  Its not THAT big, but it's quite a big larger than anything I've ever successfully soldered, and I'm not having any luck with it right now.

I haven't totally given up yet but I'm exploring the idea of just soft soldering this part.  The fabricated part won't be subject to excessive heat (i.e. not part of a boiler or fire box) and I'm sure soft-solder would be strong enough for the application.  But I do intend to powder coat the part.  Powder coating doesn't involve terribly high temps, but you do have to heat it up to 450F for about 5-10 min, then hold it at 400F for 20 min.

So, my question is soft soldering an option?  Or do you think the fabricated part will come to pieces in the powder-coating oven?

Looking for anyone's thoughts or (ideally) experience with powder coating soft soldered parts.

Thanks,
Kim

Offline 10KPete

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Re: Powder coating and Soft Solder...
« Reply #1 on: January 02, 2021, 06:19:18 AM »
Yah, dat's the prolem.

I've done a lot of power coat and a lot of "soldering". Usually not powder and "soft" together...

Tin/lead solder melts around 700*F

96/4 Tin/Silver melts are 430*F

My inclination here would be to carefully mask off the part footprint then use the 430 for the join. Pre-tin the part to be painted so the two will join instantly the solder melts. I don't think there would be much damage to the paint. It wouldn't be hard to get some scrap bit and trying it......

Also, 430 has 10 times the tensile strengths of tin/lead and is not subject to flex crystalization.

I look at every post, Kim, and love the careful work you are doing.

Pete
« Last Edit: January 02, 2021, 06:23:47 AM by 10KPete »
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Online Kim

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Re: Powder coating and Soft Solder...
« Reply #2 on: January 02, 2021, 07:10:37 AM »
Thanks Pete!
Really appreciate the voice of experience here!

Yeah, the parts aren't painted yet... I want to paint them later and am worried that they'll fall apart when baking the powder coat if I use soft solder.

Your idea of tinning them sounds good if I could solder them and paint them at the same time.   :???:\\

I'll post more about the actual situation in my thread tomorrow.  I just wanted to get the general question out to a wider audience than might be following my slow moving build :)

Thanks for following along though Pete!  I do appreciate it!
Kim

Offline Zephyrin

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Re: Powder coating and Soft Solder...
« Reply #3 on: January 02, 2021, 08:20:50 AM »
all the bodywork on this diesel shunter is soft soldered, and definitively would fall apart upon heating at these temp...
450F, is just above the melting of most tin based solder.
I also have a roll of 95% lead solder that melt at 520F, and that could do it, maybe; but the accuracy of the oven temp has also to be taken into account.

soldering tinned pieces and coating them together is a clever idea...

Offline Dave Otto

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Re: Powder coating and Soft Solder...
« Reply #4 on: January 02, 2021, 03:03:48 PM »
Hi Kim,

Why not run a test piece? Solder a couple small pieces of scrap and run them through the oven.

When I built my Moria hot air fans I wanted to have the legs and guard powder coated. I took one of the guards to the powder coater and had them run it through their oven, when I returned they handed me a small pile of parts.
This assembly was soldered with the Staybrite solder which has a 430 degree melting point.

Dave

Offline RonGinger

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Re: Powder coating and Soft Solder...
« Reply #5 on: January 02, 2021, 03:27:09 PM »
When I got my powder coat tool I made a test assembly. I had several pieces and joints- like a lap joint and a pipe/tube joint. They just about all failed in some way.

In my view soft solder and powder coat don't mix.

Online Kim

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Re: Powder coating and Soft Solder...
« Reply #6 on: January 02, 2021, 07:16:00 PM »
Thank you Zehpyrin, Dave, and Ron for your comments and advice.  Sounds like Soft solder isn't a viable route.

Although, now that I think about it, I soft soldered the tender tank together, and it didn't fall apart.  Though it was held together with screws.  The soft solder was only to make a leak-free seal along the edges.  And now that I think about it, I haven't tested it for water-tightness since I powder coated!

Anyway, doesn't sound like the right direction for me.

And just in case anyone is interested in where this came from, I just posted my update on what I'm doing and where this question comes from.  It's up on my A3 Pennsy Switcher build thread.  This link would take you right to the post with the problem http://www.modelenginemaker.com/index.php/topic,8552.msg230165.html#msg230165.

Thank you for your help,
Kim