In most cases, gold rust is due to insufficient color. Rust generally shows reddish-brown spots. Modern gold products are mostly made by oil pressure or electroforming process. Gold cannot be cleaned during production and processing. For example, gold bars bring in dust and other substances during pressing, which are easy to oxidize and form rust spots after being stored in contact with light and air for a period of time. This stain can be easily removed by professional cleaning. In addition, the process of producing gold bars is beaten with a raw hammer. If the hammer is used for a long time and is not cleaned and scrubbed in time, it may also bring in impurities and rust the gold bars.