The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Chroming Plastic Exterior Automotive Panels

We are an injection moulder of large exterior OEM automotive parts such as bumper fascias, rocker panels, claddings and grilles. A few of us are working on a project to come up with a new visual appearance for a vehicle. Our idea is to have patterned panels, bumper fascias and grille, made of plastic, and chrome-plated. We currently supply ABS grilles that go to an outside source for chroming. We currently manufacture fascias in TPO, and claddings in TPO and/or PP. Our question is, what type of material could be used for the fascias and claddings, and what type of chrome process would go along with that? If it's even feasible!

Cari Mercer
automotive injection moulder (large exterior parts) - Aurora, Ontario, Canada
2004

---

Although virtually anything can be electroplated, the name of the game in automotive application is adhesion. One reason ABS is widely plated is because pretreatment processes exist that offer excellent adhesion. Polypropylene, at least plating grade polypropylene, offers good adhesion but maybe not excellent adhesion. I don't know what, if any, pretreatment would offer good adhesion on TPO. But the book "Standards and Guidelines for Electroplated Plastics" will give you the whole story.

Another issue is plating's relative lack of flexibility. Chrome and the underlying nickel plating are relatively brittle compared to soft plastics. If these parts are soft and easily bendable, it's possible that the plating won't be nearly so.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2004

---

Hi there!

So you wanna chrome big plastic parts?....uhhhh....forget it; is my opinion.

In the past large car parts were made of steel, like bumpers. With the introduction of plastics such big chromed parts disappeared from the market, but one can find small chromes plastic car parts. Strange, isn't it? Of course it has been tried to chrome large plastic parts, but for some strange reason large chromed plastic parts did not get available. You can draw the conclusion it does not work on big plastic parts. And it is difficult, and more difficult when it comes to scaling up to industrial levels.

First plastic which was commercially plated was ABS. Tiny balls of rubber (B...butadien) are mixed in the matrix of the styrene-acrylonitril polymer. The distribution of the rubber particles can not be exactly reproduced. Unfortunately the rubber parts play a key role in the plating cycle....the get removed during etching. In the created cavity the catalyst Palladium gets bigger and bigger because nickel starts to grow on it....thus you get adhesion. When you have not a butadiene particle at the right spot you have a problem. Plating large parts?........uhhhh.....it must have been tried on industrial scale but I do not think it is possible.

Maybe you should try to silver it, with a dual spray gun. The silver has to be protected with a clear coat lacquer.

Kind regards,

Ruud Kooijman
- Venlo, The Netherlands
2004

Chroming large pieces of plastic is not a problem, we chrome motorcycle farings all the time, I would say they are relatively large, especially when compared to headlight surrounds, cell phone cases, and all the other plastic items you typically see chrome. As far as what materials to make it out of, well ABS motorcycle fairings chrome great, and you can still bend them a lot without any ill effects for the chrome, fiberglass holds up fine also... There is nothing that can't be chromed, you just have to find someone who knows how to do it.

Darius Marchal
- Ft. Lauderdale, Florida, USA
2004

Hi ~ I would like say that the largest bumper with Cr plating won't be a problem , many vehicles do such application on their decorative part, even the bumper or fascias ...etc.

James Chen
- Taiwan
2004

---

We are chroming complete cars. Body, thermoplastic exterior. The size doesn't matter. The whole system is water based. A brand new development from Germany. It works on PP and ABS also even wood is not a problem.

Ingo Gunzel / Bokem JH Chemicals, Division Canada

Ingo Gunzel
- Woodbridge, ON, Canada
2005

What is being proposed by Mssrs. Marchal and Gunzel may be a very workable answer to Mr. Mercer's situation (although making automobile fascias and claddings out of wood sounds rather impractical).

But this is a technical forum for metal finishers, so we shouldn't let people who come here for technical education leave with less understanding than they entered with :-)

There have been strides in the last few years in the development of shiny paint that the proponents may call "chrome-look", and they really are beginning to look something like chrome. But they are shiny paint, they have nothing to do with chrome and should not be called chroming; chrome is a metal and it is applied exclusively by electroplating. See our Chrome Plating FAQ.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005