Chrome problem

[Yahshu]

The chrome on a lot of my models is disintegrating. The models are in a glass display cabinet. Any ideas on what's causing it? The polar lights kits seem to be the worst off.

[cobraman]

Could be heat ? Does sunlight hit the case ?

[Art Anderson]

The chrome on a lot of my models is disintegrating. The models are in a glass display cabinet. Any ideas on what's causing it? The polar lights kits seem to be the worst off.

When you say "disintegrating", do you mean that the "chrome" is fading away, leaving the raw plastic color of the part showing? If this is happening, it's more than likely due to contaminates in the surrounding air (think air pollution here).

To understand how that can happen, it helps to understand just what model car kit "chrome" really is: For starters, it's not chromium, as would be the case on the bumpers of a real car. Virtually all the "chrome plating" on model kit parts is actually aluminum, which is deposited on those parts in a large vacuum chamber, the aluminum being vaporized in a total vacuum by the use of high-voltage electric charges shot through strips of the metal itself. The parts were sprayed (or flow-coated) with a clear, non-penetrating (non-crazing) lacquer to give the parts tree a very shiny surface, to which the vaporized aluminum molecules adhere. After this process, the kit parts tree was then given an overspray or coating of the same non-penetrating clear lacquer. This "top coat" protects the aluminum layer from wear in handling (it's only a mere few molecules thick!) and against vapors in the air. Aluminum is one of the more "active" metals on the Periodic Chart of Elements, and as such, pure aluminum (which is what is used in plating model car kit parts) "combines" very easily with elements (chemicals) that are either acidic or strong "base's" (think any acid, or a base such as sodium hydroxide here, or for that matter, even salt).

If someone in your home smokes, or your kitchen stove doesn't have a vent hood over it, the vapors (or tobacco smoke) can have chemicals in it which while perhaps invisible, can damage reactive metals such as aluminum (the sulfur compounds that can be released from cooking eggs will do that, by the way--they can tarnish silver, copper or brass very quickly).

A glass (or plastic) display case can protect the finish on your models, but in order to do so, it needs to be fairly airtight. A glass case with sliding doors will pretty much keep dust off (household dust can carry such contaminants as I mentioned and when landing on a model car surface, allow those contaminants to attack the surface finish of a model!), but still minute particles of dust can get past those sliding doors.

Other than protecting a model from constant exposure to such airborne contaminants or contaminated dust or lint, there is no really good way to protect a model. However, some modelers have been known to give the chrome parts a further clear overspray with say, Tamiya clear lacquer, Future floor polish, prior to assembly. That's not absolute proof against the plating going away, but it does go a long way to preventing it.

Of course, the high end diecast models, such as Franklin or Danbury Mint, have their plated parts electroplated with real chromium, but that is a very involved and costly process--and not one seen generally with model kit parts.

Art

[Modelbuilder Mark]

One of the other things that I know can also do this is baking soda. I have heard of people using baking soda as "snow" on a display base etc, and it will have that chemical reaction talked about above. Do you have a diorama in the same display case that may have questionable products/chemicals in it? Do you use those powders you sprinkle on the carpets then vacuum up? etc etc

Like said above, seal em up best you can. I put each completed build that is not a rust bucket or work vehicle in it's own case, then stack those where needed. Even the best glass case still let's in quite a bit of air/dust over time.

[Pro Wrench]

One question: is someone using glass cleaner to clean the glass on the case? Most glass cleaner is a mixture of ammonia, alcohol, and water. When the alcohol and ammonia evaporate, it can attach to other surfaces. Particularly if the surface is charged with static electricty, which is very common when you get dust and plastic together.

[ToyLvr]

One question: is someone using glass cleaner to clean the glass on the case? Most glass cleaner is a mixture of ammonia, alcohol, and water. When the alcohol and ammonia evaporate, it can attach to other surfaces. Particularly if the surface is charged with static electricty, which is very common when you get dust and plastic together.

Really good point.

I use cheap Ammonia (from the cleaning products aisle at the grocery store) to *strip* chrome parts when I want to paint them. Works great!

If you're getting glass cleaner anywhere near your models, you're asking for trouble...

[Yahshu]

Wow guys thanks for all the info, got a bit to keep an eye on now. I've answered each question & think we have a winner. Here's where they're kept.

This is in my man cave where I do all my building.

cobraman, No, sunlight, heat, possibly, it does get hot & humid here.

Art Anderson, It's fading away, very in depth report, thanks for teaching me something new.

Modelbuilder Mark, Now there could be a problem as I use baking soda & super glue as body filler. No carpet powders used in the house.

Pro Wrench, I'm single & live on my own, only do basic house work so no glass cleaners used

I do smoke but not in the house.

Edited October 31, 2013 by Yahshu

[slusher]

Phil, amt had a problem with plating of parts off and on in the 90's and some in 2001-03. the only reason was sealed kits l bought. lt starts with the chrome yellowing. don't know if this could be your problem..

[Pro Wrench]

^{Might want to switch to another method for filler. Maybe talcum powder or even flour}

[Nxr]

i often krylon chrome the front/back bumpers and wheels, since they would probably take too much bmf and effort to be done right that way.

I am guessing the models have some age too since they chrome is flaking? I guess time for a restoration round!

Edited November 6, 2013 by Nxr

[Tom Geiger]

Just wanted to say, don't use baking soda for anything! It's main ingredient is SALT. And salt will absorb any humidity in the air and cause reactions. Early on in my building, I followed instructions to use baking soda for rust. Later I noticed wet spots on the models during the summer / high humidity times. I've heard of other guys using spice powders for weathering. Don't do that. They'll change over time too.

[Modelbuilder Mark]

Just wanted to say, don't use baking soda for anything! It's main ingredient is SALT. And salt will absorb any humidity in the air and cause reactions. Early on in my building, I followed instructions to use baking soda for rust. Later I noticed wet spots on the models during the summer / high humidity times. I've heard of other guys using spice powders for weathering. Don't do that. They'll change over time too.

yeah, as I understand it, basically avoid things "organic" or from nature. Seems contrary to our own well being, but for model cars.......