Cost

Cost can be considered in a number of different ways for strip steels for automotive body panels. In order to achieve minimum cost whilst still providing the properties that are required by the customer we need to consider the following points:

Let's consider the issue of corrosion resistance. For automotive body panels the most appropriate type of coating is a sacrificial coating such as a zinc. There are a number of different zinc based coatings that can be used (see the section on sacrificial coatings). The selection of the most appropriate coating will depend upon the application and the required corrosion resistance. It is important that the least expensive choice is made in order to maximise profits whilst passing on the minimum cost to the customer.

Typical application	Coating type	Relative cost (1=basic price, uncoated)
Bonnets (hoods)	Electro-zinc coated steel
	ZE25/25 - 2.5ľm/side ZE50/50 - 5.0ľm/side ZE75/75 - 7.5ľm/side	1.13 1.24 1.34
Door outer	Electro-zinc-nickel coated steel
	ZN20/20 - 2ľm/side ZN30/30 - 3ľm/side ZN40/40 - 4ľm/side	1.12 1.17 1.20
Wheel arch housing	Hot-dip galvanised, iron-zinc alloy coating (Galvanneal)
	IZ100 - 100 g m^-2 min	1.20
Automotive structural member	Hot-dip galvanised
	Z275 - 275 g m^-2 min Z450 - 450 g m^-2 min	1.28 1.31

Note: A thickness of 1ľm of zinc equates to a mass of about 7 g m^-2 on one surface

The coating masses refer to the minimum coating mass, including both surfaces

Note that the real costs of a steel product will also vary according to market factors such as the strength of the currency, global availability, raw materials cost variations etc.

To minimise the cost of alloying elements whilst attaining the strength levels and formability properties that are required requires detailed control of the processing route. An example of how this can be achieved can be seen for hot rolling of strip steels.