What should I do if the mountain bike chain is rusted?

Use a rust remover to remove rust spots, then clean it with water, spray a bicycle-specific rust preventive, and then dry it naturally, then add a small amount of lubricant. No rain, no rust after two or three years of storage. If it is used frequently, add lubricating oil for about half a month. After the chain is found to be black with greasy dirt or rust spots, clean it and repeat the above steps. Except for stainless materials or sprayed special materials.