If you wish to repaint zinc coated parts, you must first remove the zinc coating using vinegar or any other mild acid.
To avoid marking painted parts during model construction two strategies are best:
Others use Horolene brass cleaner (used by clock restorers) for tarnished brass - the ammonia fumes will make you gag but the results are superb. Chemical cleaners must be washed off thoroughly as they leave a very raw finish that can tarnish again in seconds if they are not then immediately dried off. A light coating of spray lacquer can be applied to prevent future corrosion. Never use steel wool or other abrasives on brass as they give the parts a very un-natural look. This is especially important if "restoring" pre-war parts.
Zinc plated parts often deteriorate fast for a number of reasons:
George Prytulak (firstname.lastname@example.org) of the Canadian Conservation Institute (http://www.cci-icc.gc.ca) had the following advice:
Regarding the cleaning of zinc-plated parts: first try a solution of warm water and dishwashing liquid, followed by a clear water rinse and thorough towel drying. Avoid acidic or alkaline solutions: both will attack zinc. Greasy/oily contaminants can be removed with mineral spirits (Varsol, etc.)
The corrosion on the zinc will probably be either a dark grey oxide layer - which is compact and protective - or a white powdery layer of zinc carbonate. Mechanical (i.e. non-chemical) techniques are recommended to remove both. The gentlest material is a white vinyl eraser (Staedtler "Mars Plastic" or FaberCastell "Magic Rub"), available at most stationery stores. To speed things up, you can also use an electric eraser, made by Koh-I-Noor or Staedtler. There are about six different grades of eraser strips available. They range from soft, white vinyl to hard grey, ink erasers. The grey strips are the most aggressive and are best for removing rust from steel surfaces.
Fine steel wool (#0000) is another possibility, best lubricated with Three-in-One oil.
Another useful material is a Scotch-Brite (3M) pad, super-fine grade (grey) or a comparable Norton automotive hand pad (#58002 Micro Fine). These can be bought at most autobody refinishing supply shops.
To protect the cleaned surfaces and to stop them from tarnishing all over again, you might consider applying a thin coat of Johnson's Klear paste wax or Aerowax. Both are stable and easily removed with mineral spirits. Wax is best applied with clean a cotton cloth (diaper flannel is best).
The treatments described for Zinc, especially fine steel wool, can be used with Nickel.
Re-plating is an option, but it can be pricy. In theory, you can produce fine results with an inexpensive "home nickel plating bath".
Copyright 1996-2016 by David Williams.