Choice and measurement of crucial aircraft coatings system properties

All components of an aerospace coatings system must be functioning properly for it to provide all of the elements of physical protection and optical performance that it was designed to provide. To insure proper coatings system functions over its desired lifetime, one must have the capability to define, measure and evaluate those system properties that determine these functions in use. For military aircraft, the desired properties can be summarized as mechanical/chemical protection of the airframe with controlled electromagnetic emission and reflection properties. This is easily enough said, but difficult to achieve in practice. There are many possible properties one can measure on an aerospace coatings system and the cohort of designers and users of these systems are uncertain of which is the absolute correct set of measurements to choose. They seek the set that gives the maximum amount of pertinent information at the least amount of effort and expense. The sine qua non of such properties has yet to be determined, but the current "best practice" thinking among the coatings science community focuses on system flexibility, adhesion, solvent resistance, corrosion protection and camouflage optics as determined over the coatings lifetime while taking into account the effects of UV exposure, hot and cold organic fluids, sea water, humidity and temperature cycling, mechanical stressing and abrasion. All of these must be considered in choosing the tests/results protocol that the coatings/pretreatment must undergo to be "fit for use." We will discuss the current thinking on the measurements/exposures for aerospace coatings as well as the accuracy/validity that they provide in practice. We will concentrate on spectral, optical and electrochemical testing of coatings system properties and their changes in simulated and field exposure. The differences between test performance and real use performance will be considered, especially with respect to film application uniformity and film damage. (C) 2001 Elsevier Science B.V. All rights reserved.