If you judge price by the cost
of a gallon, liter or kilogram, you will not only be wrong but
may wind up paying far more than you think. That's because a
lower price for a given quantity or weight often means a higher
price per unit area of coverage.
The only valid way to compare
the cost of a coating is to compare the cost of coverage of
a given area at a specific film thickness (normally 25 microns/0.001
in.).
What gives a coating its coverage?
The answer is the amount of volume solids** it contains. And
few coatings contain the same amount of solids. A typical (and
real) example:
There are other factors worth
mentioning that are not directly related to cost/coverage:
1. Cost also depends on transfer
efficiency, the percentage of coating that actually reaches
and remains on the part. And transfer efficiency depends on
several factors, including the method of application, the configuration
of the part and the skill of the applicator.
2.The pretreatment you select
can have a significant effect on cost. And it will affect performance
of the part.
*In some industrial applications,
the coating may be only a small part of the total cost because
of the cost of the labor needed to mask, rack, multicoat and
package (as well as the cost of the packaging).
**Volume solids: All liquid
coatings contain a variety of solid materials. When the coating
is cured and the liquids driven off, only the solids remain.
Weight solids are different, so don't be confused. Some solid
ingredients weigh more than others, but don't cover as much
area. Coverage depends on the thickness of the coating and the
area covered, which is volume, not weight.
