Clear nail polish can protect gold-plated jewelry, but it is not a perfect solution. This gold layer can easily scratch or wear away. In addition, transparent nail polish can create a barrier between the jewelry and the skin, which can help slow down the corroding process.
However, if the layer of gold coating is already starting to wear away, then the nail polish will not be able to stop the base metal from showing through. Additionally, the nail polish may also discolour with time and wear, which could detract from the appearance of the jewelry. Therefore, for long-term protection, it is best to store gold-plated jewelry carefully, avoid water and chemical exposure, and have it regularly cleaned and re-plated by a professional jewelry cleaner.