Restoring Severely Pitted Pot Metal

[dencins]

This process can be used to fill pits on any part that is to be nickel plated.  I have used this before on steel and now on pot metal parts.  I used a very destroyed (eaten by acid) AE40 Butler Handle Block (1/2" x 1" pot metal) for practise.  Pot metal traps air when manufactured which tends to pit as well as creating "veins" which run deeper into the metal.  This part had a couple of deep pits that I ground out and wanted to see if they could be filled with solder. 

The first step was to use a Dremel to grind out the pits leaving a couple of larger holes.  Next was to provide a good copper electroplate surface for the 60/40 solder to adhere (picture 1).  Using a 30 watt soldering iron I applied 60/40 solder over most of the surface including the two deeper pits (picture 2).  This gets to be a bit tricky and will take practise to minimize the next step which is to file the surface (picture 3).

On a good part the next step would be to build up the surface with copper plating to get a good smoothe surafce then nickel plate.

Dennis Hallworth

[TelePlay]

Have you considered using one of those small butane torches (without the solder tip attached) as a mini blow torch to melt large quantities of solder more evenly and into the metal instead of a 30 watt soldering iron? Or would that be too hot or too much heat?

[dencins]

The first several attempts I made at this was with a small butane torch and I could not get the solder to flow on the part and it would not adhere in the holes.  Probably a combination of several things including my lack of knowledge how much heat was needed and poor soldering skills.  I eventually heated the part so hot it distorted and still the solder would not flow.

I found I could control the soldering iron better and get the solder to flow somewhat where I wanted it.  Once I get a better feel what is needed I will try other techniques but for now it is over solder and file it back.

Dennis Hallworth    

[TelePlay]

That's what I've found when trying to solder wire with the torch. It's too hot I think and the solder beads up rather than flows. You just confirmed that problem for me.

[Doug Rose]

Jonathan.....Here is a volunteer for your magic. Talk about pitted. I'm not sure if I already showed this to you...Doug

[dencins]

Doug

I remember those parts.  In fact it was one of the reason I started to work on a process for heavily corroded metal.  I should be able to work on those now that I have a method to address the corrosion. 

I think these were originally painted black.  Is your plan to paint them after the corrosion is fixed?  I should be able to fill the pits then put on a copper layer that can be painted.

Dennis

[Bill]

Nice work, Dennis!

I've found a torch to be hard to work with, too. Part of the problem is that the flame has two parts - an oxidizing flame and a reducing flame. If you get the wrong part of the flame on the part, it deposits soot and you are done.

Did your solder have acid flux (plumbing solder), rosin flux (electronics solder), or no flux? Would it help to use liquid flux that you apply with a brush?

Bill

[Doug Rose]

Doug

I remember those parts.  In fact it was one of the reason I started to work on a process for heavily corroded metal.  I should be able to work on those now that I have a method to address the corrosion. 

I think these were originally painted black.  Is your plan to paint them after the corrosion is fixed?  I should be able to fill the pits then put on a copper layer that can be painted.

Dennis

Dennis....I'd want to have it plated. It wouldn't have to be perfect, but a chrome or nickel plate would look sharp....Doug

[dencins]

Bill

I am using 60/40 rosin core solder - it is what I had available.

I was thinking about using a liquid flux but it can not be acid - too much risk on pot metal which reacts with acid.  Is there a liquid rosin flux you can recommend?

I was also wondering if I should use solid core rather than rosin core.  Any opinion?

Dennis Hallworth

[dencins]

Doug

It can be nickel plated over the copper.

Would you provide a picture of the other side of the plate that has the switchhook?  I see six rivets but do not know what they are holding.

Dennis Hallworth

[Doug Rose]

Doug

It can be nickel plated over the copper.

Would you provide a picture of the other side of the plate that has the switchhook?  I see six rivets but do not know what they are holding.

Dennis Hallworth

Hey Dennis....Here you go....many thanks...Doug

[dencins]

It looks like the pin can be pushed out to remove the switch hook so then I can remove the insulator.  I suspect the switch is held on by screws?  Is the terminal block also held on by screws?  If they are I can do the rest as one piece unless I am missing something.

Dennis Hallworth

[GG]

Excellent results, Dennis; I would have thought that AE hookswitch block was a total loss.  As it is, it could be plated or painted and look fine.

Question, slightly unrelated:  What's the toughest (scratch and chip resistant) type of paint that can be used over metal and what about over plastic?  Is there anything tougher than powder coating for use on metal?   

[dencins]

Excellent results, Dennis; I would have thought that AE hookswitch block was a total loss.  As it is, it could be plated or painted and look fine.

Question, slightly unrelated:  What's the toughest (scratch and chip resistant) type of paint that can be used over metal and what about over plastic?  Is there anything tougher than powder coating for use on metal?   

Thanks.  Sadly there is quite a bit of material and detail on the bottom side that has been lost and is not worth trying to recover which is why I used it for practise. 

I will let someone more familiar with paint and powder coat respond to your questions.

Dennis Hallworth

[Bill]

I am using 60/40 rosin core solder - it is what I had available. I was thinking about using a liquid flux but it can not be acid.  Is there a liquid rosin flux you can recommend?
Dennis Hallworth

Dennis -

Liquid or paste rosin flux is certainly available from any number of suppliers, including Radio Shack. I have no idea whether it would be better for this application than rosin-core solder. Somehow I always felt (with no backup) that it would be better to get the flux on the workpiece before heating it, so that the flux keeps the surface clean and un-oxidized as the temperature rises. But again, I just don't know.

Bill