Just as it is good practice to wash store-bought vegetables before eating them, and wash new clothes before wearing them, it is good practice in metal finishing to "wash" plating tanks and anything we put in them to prevent potential contaminants from spoiling the plating bath.

Usually though, soap and water is not used. Instead acid or alkali appropriate to the plating process is used, on the theory that if the contaminant will be drawn out by the plating solution, it will be drawn out by the acid or alkali of the plating solution.

This cleaning process is called "leaching".