Flash Copper

[Frank39]

Can you take a diecast part that has been plated with flash copper and sand then plate it again with flash copper.
Thanks Frank

[minord]

Sure. You just have to make sure it's SUPER clean. Use Nitril gloves too. Anything else will leave a residue on your part that will drive you nuts!

Minor D

[Frank39]

How do I super clean the part prior to plateing? I have tried several times and they have not come out . Any help would be appreciated.

[minord]

Hi Frank........

With pot metal, the only thing that seems to work is to sand blast, rinse with distilled water, then immediately plate in flash copper @110-120 degrees @.03 DCA per sq.inch.

look for a post in this section by 48Buick. This guy has written the "Bible" on pot metal plating as far as I'm concerned.

Once you get the copper to hold, it will be difficult to even sand blast it off!

Good luck, hope this helps!

MD

[minord]

One more thing Frank.......

Make sure you're using PURPLE or BLUE NITRIL gloves. Any medical supply or home care supplier should be able to get them for you. I pay like $14 for a box of 100. I can't stress this enough!

I'll venture that 95% of my problems EVAPORATED when I started doing this!

Later.......MD

[fxstcguy98]

Frank
After plating with Flash copper, sand lightly with 600 grit, wash with HOT water and Dawn or Polmolive, SP degreaser, then put it in pickle#4 just to make sure the copper is activated, then back in the Flash copper. Make sure you pass the water break test first. Hope this helps.

[dadkar2]

I have read and tried everything in the book on vintage pot metal (60-90 year old vintage!!). The important theme to remember is that ANYTHING corrodes pot metal--even tap water. Once it corrodes (oxidizes) even a little, it is reluctant to plate. Even the plating solution will corrode it if you let it. By far the only thing that works reliably is:

Sand Blast with 180 grit aluminum oxide to remove ALL traces of corrosion and previous plating. Use an eye loupe to inspect even into the deepest pits. Do not relent until every trace of black corrosion is GONE. If you don't own a sandblaster, stop here. Don't work with pot metal until you buy one. You can get a very serviceable unit for around $120 and use it with a decent shop vac to keep your shop dust free.

Thoroughly blow off the dust residue. Be very thorough. Use a water and oil filter in the line. Do not rinse in water. Do not let the part sit around after this for more than a few minutes. Proceed immediately to the next step.

Drop into the flash copper (Alkaline copper) tank live (eg, have the suspending wire tied to the power supply with a test lead so it is powered when it touches the solution) at about 500mA per square inch, for only 15 seconds or so. Then turn current down to 60mA per square inch. This causes the part to plate before the alkaline solution can begin to attack it. Leave in solution at 60mA per inch for 1 hour.

Don't be tempted to go into the acid copper bath anywhere through this process. If you need to do pit repair, now's the time. Use regular solder paste over the copper ONLY and only heat as much as it takes to just melt the solder in. Degrease thoroughly in lacquer thinner, then sand the solder smooth with 320 grit. Try not to break through the copper, although it might be hard to do in a few spots. In any case, minimize it.

Sand carefully between the following coats with 400, but stick with the flash copper throughout the whole process. Sometimes I prefer to do 1 hour copper, light sand, one hour of copper, then solder repair. It builds up more copper and makes it tougher to sand through.

It may sound like a pain, but wet sanding with distilled water is a great insurance policy for 60 cents a gallon. If your tap water is slightly acidic, it may oxidize the surface of the pot metal enough to cause blistering later.

Cleaning between coats and after degreasing with lacquer thinner should be done by hand with a toothbrush and a fresh batch of SP degreaser. I agree with fxst on this: You MUST pass water break. SP Degreaser mixed with distilled water with ultrasonics is another alternative I have tried with some success. Avoid heating. I have abandoned dishwashing liquid because some of them leave residue.

Also, any time you break through the copper, make sure the bare pot metal is shiny and clean. Do NOT let the part sit around for more than a few minutes once this happens. Get it into the plating solution again, and dip it in LIVE.

Stay away from pickling throughout the process. I have found that it is not necessary if the part is clean and oxide free. It will be relatively oxide free if you have just thoroughly sanded it. The reason is if you break through the copper you'll cause the pot metal bare spot to corrode in the acid. It's not worth the risk.

Get about 3 hours of plating on there before you buff, sanding between 1 hour sessions.

After buffing, clean very carefully as before. Then plate in flash copper for 20 minutes. This will plate up any minute, possibly invisible spots that may have gone bare from buffing. Little edges and corners are always suspect.

Rinse part completely (two separate, consecutive rinses) in distilled water...keep it wet....drop into the nickel plating tank the way you'd nickel plate any part.

I have not had a problem with the latex gloves I use, but minord's advice is well taken. From my experience with semiconductor fabrication, I know that many of these gloves will leave behind some pretty nasty silicone oils and other contaminants. I know that I've been lucky on this one. I plan to buy nitrile gloves asap. :P

I have not yet tried pre-plating the raw pot metal with zinc, but that is on my list of things to try. But right now, what I have listed above is working!

I realize that even the above may not be perfect, but this seems to bring me results closest to perfect, reliably. Be patient with pot metal. The older the pot metal, the harder it is to plate.

Kind regards,
Ken

[minord]

Just as sort of an addendum to Ken's remarks, I've found the simplest way to degrease pretty much ANYTHING..........and especially pot metal, is either "Soft Scrub" or a super product made by Castrol called (wouldn't you know it) "Super Clean". This "super Clean" comes in a purple jug or spray bottle and is easy to spot at any NAPA , or simular Auto Parts store.

Fact is, I'm so paranoid about pot metal, I use "Soft Scrub" and a toothbrush, then I rinse really good with "Super Clean", then rinse REALLY good with distilled water.

I do however agree with Ken 100% on the initial dip procedure. After sand blasting, (don't forget the nitryl gloves) blow your part off with filtered air and go immediately to flash copper with NO RINSE.

I've also found this works better than using the nickel strike, (pot metal primer) as it seems to bond much better to the base.

Acid copper will definitely speed up the build process for smoothing, but using only the flash copper is fine until you get a better feel for what you can get away with on the sanding and polishing without going through the copper.

MD

[KCV6]

What has worked for me.

Alkaline chrome strip if there is chrome, dremel any real bad dark pits lightly, don't make more work for yourself then needed, Citrus acid based cleaner and scrubbing brush. Activate like it was zinc, i.e. in 10% sulphuric solution, chloride zinc heavy and sand and repeat zinc, zinc is cheap and forgiving! then flash copper heavy and take it from there.

I have used flash copper over sanded through flash copper on zinc plated pot metal, I have even put more zinc over copper then sulphuric activated the zinc. If you can get a clean layer of zinc on zinc diecast first it all becomes much easier.

Don't forget the various degrease and rinse steps in between

Downside.... You need a zinc setup as well, but zinc is very usefull and often overlooked as the enemy when it comes to copper and NiCo plating.