Silver-plated metal items have a coating of either pure silver or sterling silver on the outside. Silver-plated items include jewellery and kitchen flatware, and although they do not have the same value as silver, the silver-plated items tarnish and turn yellow just like pure silver.
Silver plating consists of applying a thin outer layer of silver to a metal item to give the appearance of being made completely of silver. Although the outside silver plate layer is thin, the chemical properties of silver plate still react the same way to chemicals, which can cause discolouring.
When silver comes into contact with sulphides like sulphur dioxide, it begins to turn yellow. This is the first step in the tarnishing process, while further tarnish will turn the silver a purplish, grey or black colour.
Tarnished, silver-plated items need to be cleaned as they begin to yellow to prevent the tarnish from embedding deeper into the structure, which makes it harder or impossible to remove. Since the yellowing of silver-plated items is caused by sulphides coming into contact with the surface, dipping the item in polish will help remove the yellow tarnish, without removing the silver layer.