No Good Polishing Instructions

[jf]

I've successfully plated over steel and zinc with copper. Buffing has been a frustration. First of all, sandblasting off old chrome does not work with glass beeds. You must use the black stuff (silicon carbide?). (Not explained in Caswell instructions). When you use the black stuff it leaves a rough finish, so then you have to sand, sand, sand before buffing. OK now on to buffing. I'm using the white compound as recommended by Caswell. The black gunk (compound) created while buffing sticks to the part. Some have said that the part is not hot enough and the compound is not liquifying. If I put enough pressure on the part to heat it up, that wears off the copper and I have to replate copper. Buffing is not rocket science so do I have bad compound, bad buffing wheels or what. What am I doing wrong...too much compound?, too little compound?, wrong speed?, too much pressure?, too little pressure?, too hot?, too cold?. Somebody out there has to have a source for buffing instructions other than Caswells, which are worthless.

[mpierich]

Originally Posted by jf

I've successfully plated over steel and zinc with copper. Buffing has been a frustration. First of all, sandblasting off old chrome does not work with glass beeds. You must use the black stuff (silicon carbide?). (Not explained in Caswell instructions). When you use the black stuff it leaves a rough finish, so then you have to sand, sand, sand before buffing. OK now on to buffing. I'm using the white compound as recommended by Caswell. The black gunk (compound) created while buffing sticks to the part. Some have said that the part is not hot enough and the compound is not liquifying. If I put enough pressure on the part to heat it up, that wears off the copper and I have to replate copper. Buffing is not rocket science so do I have bad compound, bad buffing wheels or what. What am I doing wrong...too much compound?, too little compound?, wrong speed?, too much pressure?, too little pressure?, too hot?, too cold?. Somebody out there has to have a source for buffing instructions other than Caswells, which are worthless.

I'm not a plater, but:

The buffing compound is sticking because the part is still too rough for that compound. When I'm polishing aluminum, as soon as I see white rouge sticking, I immediately go back to emery compound to get out the unseen scratches that I missed the first time.

If you have to polish that much after the plating, the part was too rough to begin with. You need to do all your smoothing _before_ you plate. It is my understanding that the part needs to be _polished_, not just sanded, before plating begins. Furthermore, once it's completely polished I do believe it's to be chemically treated to give it some tooth (but not roughed up) before plating.

Have you asked this question in the plating forum?

P.S. - I have successfully used greaseless compound to remove chrome plating (the finest grit that will work), although it may be rather time-consuming if the part is of a complex shape. I also understand that you can somehow use the plating equipment to "reverse" the system to remove the plating electrochemically.

[jrow]

jf,

Outside of what Mike said (mpierich) which is very accurate info. You have answered your own question. The hotter you get the metal when polishing the more apt you are to have the copper come off. Instead of sanding after you media blast try using some greaseless compound on a buff, much quicker. You might try using either SS compound or Tripoli in lieu of Emory.

John

[baz]

first i would not sandblast the chrome off , there are other ways of doing that won t damage the material as much .
blasting chrome off on alumiium could seriously damage some parts .you are trying to blast a very hard material with very abrasive media on a very soft material.
i also think like mpierich said ,(If you have to polish that much after the plating, the part was too rough to begin with.)

[chromo]

Sorry, I have to disagree, Caswells instructions ARE NOT worthless! They are good, also the plating manual is good, if you have it then read it. If not, maybe buy it? I have the older manual from years ago and still read it at times, lot's of good stuff in there.

WHY are you BLASTING chrome off parts? That's my first question! Maybe you have a reason?
You don't really say what your trying to plate on your parts either or type of parts, Silver, gold, brass, new chrome, etc... Car emblems, door handles, water faucets, bumpers?
You can simply remove the Chrome top coating and leave the Nickel which is under the chrome. If the Nickel is not pitted or other damage polish the nickel and plate over it. I forget what all plates over the nickel, I know I was removing chrome, polishing, then gold plating over the original nickel.
I think I did plate copper over nickel to fix defects, buff/polish, then plate over the copper again, been awhile since I did such though. That was like repairing a car bumper just to make it look decent but not show perfect.

It's been awhile since I did much of this, but as I recall it may have been reverse currant and battery acid that electrically removed the chrome and did not harm the nickel under it. It's in the plating manual I beleave. Most everything I did like this was steel parts perhaps some pot metal, no aluminum stuff though that I recall.
I had the online download version of the manual, it's on my other computer which is not working at the moment or I would look it up for you if it would help.