Hi Guys,
I have a bit of a problem with a bunch of 1/35 scale cast metal figures by Soldat made in Spain.
The metal figures are all in their original packaging, which is not airtight.
All the figures have a whitish coating on them, like a thin wash of white paint. The helmets are separate and are more solidly coated with white. The separate rifles have no coating at all and are a silvery metallic color.
Is this normal or is it a oxidization problem.
What can I do to clean them back to a silver color?
I tried soaking one in white vinegar which is 5% acid. Then I used a tooth brush to try to rub the white off. Very little improvement.
Then I tried muriatic acid which is a stronger acid (32%) which worked fine but the resultant color was a very dark gray.
Is this dark gray color the best that I can expect?
I plan on washing the figures with detergent before painting them. Is this the correct thing to do or should I do something else to prep them?
Any explanations as to what caused the white covering?
Any suggestions on how to get rid of the white coating?
Thank you,
Stephen

Just a guess, but years ago, with the older alloys used for white metal kits, you could run into what was called "lead rot". It was essentially oxidation that if left untreated, would consume the kit leaving behind a pile of powder and dust. It sounds like that could be what you're experiencing. The best bet is to scrub off the oxidizing metal at the surface with an old toothbrush and some toothpaste (which is a mild abrasive). It goes without saying, don't contaminate your toothpaste with white metal and that old toothbrush can never come into contact with your mouth again, but once you've successfully cleaned the kit of all of the oxidation, wash it, quickly dry it, and prime it right away to "seal" it. That should keep any further oxidation from developing. You can google for more information. Here's one result from google:

http://theminiaturespage.com/boards/msg.mv?id=152257

There is another aspect to this problem. Many years ago a lot of the parts for model ships were cast in lead or in a lead rich white metal alloy. Then these parts were painted when on the model. Over the years the paint coating cracked, due to changes in temperature. vibration, etc., and moisture worked its way in through the cracks in the paint. Some years later the paint was the only thing that held the shape as the insides had turned to powder (lead oxide). Manu ship museums have been struggling with this problem because their prize models are falling apart. We are talking about some of the bigger an better museums, like in Washington DC. They have been running studies on how to combat this. I read one long paper on it a few years ago.
Suffice it to say than when making parts for models these days cast resin may be better in terms of long life than the old White metal materials.
With different model part manufacturers not letting anyone in on the formulations of their casting materials, assuming they themselves even know, it is all lots of luck for us modelers.
As to these soldat figures I have, I am going to assume that they have all been painted in a white slip o a paint to protect them and I will simply paint over them.
Thanks,
Stephen