"If the parts are not corroded they many be cleaned with soapy water or white spirits.

However if rust is apparent, the part must be either painted or re-plated.  The easiest way to re-plate is to find a local engineering firm who will do it for you.  Platers will remove all the previous zinc coating whether corroded or not, using chemicals, before replating, so there is no need to do it yourself.

Once you have used zinc plated parts they should be rubbed down with light oil to stop corrosion starting.  Sewing machine oil is a good option.  The salt from your skin is enough to start corrosion.  Wrap zinc plated parts in oiled paper to prevent precipitation  if they are to be stored in oak chests and any oak boxes.  Woods and especially oak, give off an acetic gas that corrodes the plating.