moisture diffusion in coatings on metal  

Posting by bernard schultz on May 31, 2008 at 21:29:01.

Hi All:

My question is about moisture diffusion in polymer coating and paints on a metal alloy aluminum surface. I am interested in coatings used in aerospace application, i.e. the coating on the hull of a Boeing 747. However I am unaware of the industry standards with regard to expected life time of the coatings in normal operating conditions.

More specifically:

-Does water from the atmosphere diffuse in such a coating to a significant extent?
-Does the moisture reach the interface between coating and metal,
- Does this lead to subsequent loss of adhesion and/or chemical degradation or corossion of the metal below?
- Is temperature spiking a problem, are - in the design phase - cycling tests performed which include freeze thaw cycles?

The atmosphere at 10 km height is totally different from ground level. Water is absorbed on the ground and is desorbed when airborn? Is the coating thickness based on the lag time coating-metal for water diffusion?

- How do carbon fibre epoxy composites compare to coating on metal solutions?
- How does carbon fibre epoxy resin compare to fibre metal laminates, such as Glare?

Many thanks for your assistance.


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