Chromeing plastic parts

Home telescope makes once used a chemical method to deposit silver on their hand ground mirrors. Unfortuantely, it was a risky and toxic procedure. And silver tarnishes. I'm sure you can find the recipe in old telescope making books.
Model parts are chromed by vacuum deposition. Parts are stuck in a vacuum chamber and chromium is vaporized inside. The vapor "condenses" and plates out on everything it touches.
Look in the phone book for chroming services. You should find them. The car and motorcycle restorers use them all the time. I know one guy who plated a plastic model this way. It wasn't cheap, but it came out pretty cool! The look isn't what you'd want for anything other than a pampered, hand polished aircraft - like a race plane.
"Galvanizing" is a zinc dip process to prevent corrosion. Not what you want at all.
Greg Reynolds, IPMS

I won a ChromeTech USA gift certificate that's worth $20 and expires Sept. 04. I will most likely never use it. Rob Gronovius Visit my motor pool in the gallery

There apparently is a way of electroplating plastic parts! The "medium" and "high" end 1:24 scale diecast model cars & trucks coming out of China from such as Yatming, and those from Franklin Mint and Danbury Mint have such details as plastic grilles, bumpers, side-spears and hubcaps actually plated in chromium over copper!b I learned this some years back when reworking a Franklin Mint 1949 Buick Roadmaster convertible (crunched) into an Estate Wagon (station wagon). Tried to cut away a mounting pin from a bumper, found it extremely tough to grind through, you guessed it, chromium (which is quite hard) and once through that, found copper, then plastic.
I do know that auto makers use chromium plating on plastic parts, such as grilles and interior trims, have a fine line scar on my left thumb where the chromium plate on the end of the windshield wiper stalk knob of my '90 Plymouth Grand Voyager came loose at about 70mph just as I reached to turn on the windshield wipers in a sudden thunderstorm.
Actually, I had an engineer from Ford Motor Company explain the process to me while on an airline flight to Detroit in 1977, wish I'd taken notes! This was new technology at that time, according to him.
Art Anderson

Hi Art,
That just leads to the question: "how do they get the copper on??" -- Dennis Loep The Glueing Dutchman
"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny ...'" Isaac Asimov

Had a friend whose family business included vacuum metalising of plastic components, ( mostly Xmas decorations, perfume bottle tops etc. ) Components were first given a couple of spray coats of lacquer to obtain a high gloss finish and placed in Vacuum chamber. Under vacuum, pieces of aluminium wire were vapourised whilst the components were mechanically rotated ( to get an even coverage. ) Final part of the process was to give components a further lacquer coating to protect the very thin and easily damaged metal coating. Sometimes this top coat was dyed to look like brass or copper ( Handy for model ships ) or coloured for Xmas decorations.. I Don't know if the kit makers use this particular process
bassa who is at clear dot net dot en zed

I got the impression that it's not that different from normal electroplating of metal parts; the trick is to make a conductive plastic (so you can run a current through it) that's thermally stable (so the chrome doesn't peel off in service).
Steve H
Bert&Ernie wrote:

8 I got the impression that it's not that different from normal 8< - - - - - - -
Hi all thanks for all the info. I learnt that there ar about two sorts of plating:
1. Electroplating where first chemically a layer of copper is put on the plastic which can after that be plated.
2. Vacuum Metalizing (which gives the result I was wondering about in the first place) where vaporized Aluminum will be deposited in a vacuum on the plastic parts.
Bad thing is that is virtually impossible to do this at home.
BUMMER!

Uh... please don't! Besides toxic, the mixture can be very dangerous (it can become explosive) not to mention expensive - you need a fair amount of silver nitrate. The resulting coat will probably be uneven, and will require polishing to bring out the shine (easy to do on a mirror, tough to do on a complex shape). you then have to seal the surface with a clear coat (to reduce tarnishing).
I think it's actually aluminum. Cheaper and safer. At my old job, I put a couple of non-mirror parts in a big aluminizing chamber (a penny... and a dead spider) and the results were impressively shiny.
Expensive, but probably the cheapest & safest in the long run. Maybe a local group of modelers can share the expense of a group chrome run.
Frank

You are correct.
Most plastic kit manufacturers use the Vacuum Metalizing like it is described in the thread about Christmas ornaments. And yes, the "chrome" is really Aluminum deposited over a shiny lacquered surface. It does look very close to real chrome.
The other method (also described in this thread) used by many off-shore model makers and it is real Chromium.
I'm not familliar with the process but I would assume that there is a layer of conductive laquer applied to plastic, then a layer of copper is deposited (same as when the real car parts get plated). Then a layer of Chromium is applied. This is done via electroplating.
Neither of the methods is really suitable for a do-it-at-home hobbyist. Electroplating is messy and uses some nasty chemicals.
Vacuum Metalizing requires special equipment (I'm sure it is expensive).
But I know of 3 places which will Vacuum Metalize parts for you.
ChromeTech USA (still in business) Little Motor Car Company in USA (not sure if they ars still around). The 3rd place was in Canada (and I don't recall the name). All American Resin was using them for their plating.
As for electroplating, check your Phone Book under PLATING and make some calls. You might get lucky, but the minimum price might be quite high.
There is another alternative. Use Alclad II Chrome paint. It is for airbrush only, but if you follow their instructions you'll end up with a very nice looking chrome like finish. Not exactly like the other methods, but pretty close. And you can do it at home.
I don't have any URLs handy but I'm sure you can find all you need using a Google search.
Peteski

Hi Peter,
I already have an adress for "normal" elctroplating where I used to bring my car modeling parts from the time I was still producing model car kits.
As I am starting a new line of models (and always looking for cheaper methods and trying to do everything myself) I was just wondering how "the other" system worked and see if it could be done at home. Turned out to be not the way.
For small production runs Allclad is not an option.
Thanks for the input.
-- Dennis Loep The Glueing Dutchman
"The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' but 'That's funny ...'" Isaac Asimov

Actually, Eastwood, the 1:1 car restoration supply people, do offer a "table top" electroplating outfit, which will electroplate copper, chromium, nickel, even brass and gold, at very nomimal expense. The real car people have been using this sort of setup for almost as long as I've been around (50+ years and counting).
This system involves a small DC rectifier, the electrolytic plating solution, a brush and ground contact which does the job.
Yes, the chemicals involved are nasty, but they come in such small quantities, that disposal really shouldn't be all that much of a problem.
As an aside here, as a 7th-grader (dadgummit, that was way back in 1956!), in shop class, we had to learn how to solder. The flux we used was copper sulfate in solution. We used ordinary water color brushes to apply the copper sulfate to the sheet steel we were assigned to solder, and guess what? The copper sulfate not only plated copper on to the sheet steel, but also onto the ferrule of the paint brush.
Now, all one has to do is come up with a conductive, sprayable coating for the plastic parts, and I should think we'd be on our way?
Art Anderson