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Metals
Plated iron
Iron may be plated with zinc, as in galvanised iron or tin, copper, chromium or nickel. These coatings protect the base iron sheet from corroding, and also provide a bright surface finish.
Corrosion of plated iron
Corrosion usually occurs after the breakdown of the surface plate. This exposes the iron, which then starts to rust.
Treatment of plated iron
To remove the rust, a citric acid solution containing an inhibitor can be used. The inhibitor is included to prevent any attack on the plating metal.
The solution is 10g of thiourea and 50g of citric acid in 1 litre of water. Thiourea is the inhibitor.
Test the solution on an inconspicuous area of the object, or on a scrap piece of the same material, before proceeding with the treatment.
Following removal of the rust, dry the object by dipping it in three successive acetone baths. At this stage, or earlier if there are no rust problems, the plate can be cleaned with industrial methylated spirits. Corroded areas can be removed with a mild abrasive such as pumice powder in methylated spirits.
| CAUTION: |
| Check your chemical safety data sheets, and take the appropriate precautions. |
Coating plated iron
If a bright surface finish is required after cleaning, a proprietary metal cleaner can be used as a once-only polish. The artefact can then be coated with a clear, acrylic lacquer.
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