Solutions to problems electroplating ABS-PC, polycarbonate, PBT, & other plastics

A. Plating on ABS/PC is possible but you need a special preconditioner before the chromic etcher. Ask your supplier about it.

A. Hi Miguel. A starting point in troubleshooting is to look at the back of the peeled foil and the part of the workpiece which has peeled, and determine what layer separated from what layer. While the plating sometimes peels completely, there remains the chance there was peeling between the electroless nickel or other prepates and the silver or gold.

But assuming that the plating peeled all the way down to the plastic, first, you'll want to check with GE to make certain that they consider Velox 420 a "plating grade" of resin. Second, you'll want to align yourself with a supplier of the process chemistry who would have the required knowledge base, or a plating shop who is good at this application.

Plating on plastics, especially on hard-to-plate plastics, is something that is learned from years of experience after acquiring a good deal of book knowledge. I don't want to make it sound like black magic, but there are many critical steps, any one of which can lead to this poor adhesion or appearance. While inadequate etching is usually the first suspect, it's far from the only one.

A. Dear KUMAR,

Chromic/sulfuric acids etchant will work for ABS/poly carbonate but to increase the adhesion it is better to use pre-etch solution. For polycarbonate it has the following composition:

tri ethanol amine 100 gm/l
ethylene glycol di ethyl ether 80 gm/l
sodium hydroxide 150 gm/l.

Best regards

A. That mixture should do the job. I suggest you run it at about 50 °C and etch for between 15-20 minutes. Make sure you destroy all the hexavalent chromium before going into the plating tanks or it will blister, peel, skip plate and generally fail. I suggest you reduce the chromium to trivalent chromium by washing in sodium metabisulphite for about 10-15 minutes, followed by thorough washing in counterflowed clean water.

A. Plasma discharge is a process whereby a plasma is struck in a low vacuum. The vacuum is typically less than 250mT. The most useful gases for ABS and PC are oxygen, nitrous oxide or air. Suitable powers for polymer activation are in the order of 80-120W and processing times between 1 and 5 minutes, depending on the polymer.

A. Marbo,

It is possible to plate Ni Cr over PC ABS blends. The etch is critical. So is the selection of a Plating Grade PC ABS blend. Etch in 450 gpl CrO3 + 300 GPL H2SO4 at 70 °C for 6 to 10 minutes. Or more if needed. This is the major aspect. Rest is similar to your process already being followed.

Regards,

A. By mechanical weakening, I presume you mean the chrome plated plastic is more prone to failure than the unplated counterpart. This effect is well known in the POP sector and initially caused a lot of problems. Many of the POP practitioners have got over it in their own way, but one way I know of is to use only a very thin layer of electroless copper or nickel, thicken this with about 5 microns of low stress copper, followed by about 15 microns of low stress nickel. Decorative chrome can be put on top of this. Hopefully, others will give alternative methods of increasing the mechanical strength of plated plastics, as I cannot be sure this is the best solution!

A. Dear Mr. Tse,

Plating ABS/PC is too complicated to discuss here in detail. Contact the supplier of the plating chemistry, as they should be able to help.

Regards,

A. Have you tried stop off paints to protect selected areas?

A. Have you tried to use preplating strips?

A. I am having similar problems masking a totally ABS moulding! On the blistering side of things you must ensure that it is a plateable grade of ABS, ensure that there is no pigment, make sure it is not 're-grind' material and also that the surface is not stressed. Try to get more copper on the part as this seems to act as a dampener in thermal expansion. Also ensure that the initial etching material is not at end of life.

A. Virtually anything can be plated, Ken, but the usual problem is that excellent adhesion is required, and that can be difficult to achieve between plastic and metal unless excellent "keying" through etching is possible. ABS is special because it can be etched in a way that leaves a sponge-like surface for great adhesion. I would suggest looking at "Standards & Guidelines for Electroplated Plastics", which will give you a fuller understanding of the issues and help you make a decision on how to proceed.

There are ways to electroplate polycarbonate, but as far as I know, none offer durability and adhesion comparable to plating on ABS. Then again, firms like Ekem specialize in processes for plating on polycarbonate and know a lot more about it than me.

A. Hi, Lajos. There are many competing technologies for applying a shiny metallic-looking coating. The choice depends on how shiny, plus how much wear resistance and adhesion is required. The majority of brightwork on automobile headlights and taillights, protected from the environment is probably vacuum metallizing and relatively cheap when done in volume. But on grills and exterior plastic parts it is chrome plated plastic, which is relatively very expensive. but for top adhesion you need a plastic designed for that, like ABS (I don't know if Valox is selectively etchable like ABS to bring out excellent "tooth"). Other possibilities include chrome-look paint. Single-sided coating should not be a problem with any of the technologies.

Good luck.

Regards,

A. Valox 420 SEO is a PET-PBT blend of polymers with 30% glass filler. It is possible to etch PET/PBT, but it takes some very aggressive processes. I would suggest that 420SEO is not the best material for metallising, but it will be pretty strong!
I seem to recall that GE, who originally marketed Valox, would supply it with a range of fillers, including calcium carbonate.
I would suggest that you contact the current suppliers of Valox (I believe GE recently sold off its plastics division to SABIC) and see if they still do the filled version of Valox and if so, what fillers are used. Depending on the fillers, you can pre-select your etching process to meet your needs.
Your other questions are very open ended and need to be addressed with some technical knowledge and understanding of end-uses. I would therefore recommend you take Ted's advice and get some background information on plating plastics before wanting a long series of information on a complex topic. I am sure you will be able to achieve your highly reflective surface, but you need to know what your budget is and what the product's end use will be

A. It could be temperature, what with the warm summer weather. Maybe try running the parts in the morning. You can also use less bath time but I suppose you've tried that. What you might be seeing is varying base material. That's pretty common for the type of material you are working with. You may need to write an ECO or allow a temporary deviation and try a less concentrated solution (below approved range) but that would need to be tested. Good luck, you can do it. We're all behind you.

A. Dear Ana,

If the plater says it must be the moulding and the moulder says it must be the plating, you don't have a root cause, you have an argument.

So some questions for you:

What are "spotty speckles", exactly? From your description it's hard to tell if they're little pits, blisters, discolouration...

Do these problems always appear at the same stage in the plating process or the same region of the parts? Are they genuinely all the same type of defect or have people gotten into the habit of labelling all small defects under the one category?

Has anything in the moulding process changed? Can you document this?

Has anything in the plating process changed? Can your supplier document this?

How are parts packaged and handled as they're moved between you and your supplier?

A. Hi Kapil. Unfortunately, many things can go wrong and lead to peeling. But I would suggest starting by reading about etching of PC+ABS on this thread and getting back to us with follow-up questions.

Luck & Regards,

A. I assume you are following the standard procedure for POP including EN/EC, etc.
ABS PC needs a more concentrated and more etching time than ABS.

A. Hi.

Although plating is complicated and there could be other causes, it sounds like the first things to investigate are how much PC is in the blend, and whether the pre-etch and etch are adequate for it.

Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

• Topic #18069 "Plating on Plastics: ABS vs PC, Nylon, & other plastics -- What substrate to use?"