Two methods are used. Heat
treating and shot blasting. Both may be used in combination.
If required the material
can be heated in a large gas or electric powered oven for a set time. This is
usually only required for very hard steels. (this is a rare requirement)
Most hard steels are pre-treated
by shot blasting the surface immediately prior to plating.
When an item is chrome plated,
gas is trapped in the plating. If this is not released in a controlled manner,
problems may occur when the item is used. Such a problem can occur with a roller
used in the manufacture of plastic sheet, as the sheet is passed over the roll,
the gas escapes causing small bubbles or holes to appear in the product.
These gases can be removed
by heat treating in an oven immediately after removal from the plating vat.