Coating for Aluminum Alloy Aerostructures

A method for processing an aluminum alloy substrate (22), the method comprising:

• boric-sulfuric acid anodizing (BSAA) leaving porosity;
• immersion infiltration of a sealer (36) to partially fill the porosity;
• spraying a first primer to further fill the porosity;
• and
• spraying a second primer, more viscous than the first primer.

An airfoil element (20, 100) comprising:

• an airfoil (102) having a pressure side and a suction side;
• an aluminum alloy substrate (22);
• a first coating system (23) atop the substrate and comprising on at least 20% of the pressure side:
• an anodize layer (24) having a thickness (TA) of 1.0 micrometer to 5.0 micrometers;
• a sealant (36) filling at least 5.0% of porosity in the anodize layer;
• one or more primer layers (40, 44);
• a polymeric coating (48) atop the one or more primer layers having a thickness (TT) of 10.0 micrometers to 1.0 millimeter;
• and
• a second coating system atop the substrate and comprising on a majority of the suction side:
• an anodize layer (24) having a thickness (TA) of 1.0 micrometer to 5.0 micrometers;
• a sealant (36) filling at least 5.0% of porosity in the anodize layer;
• one or more primer layers (40);
• and
• lacking a polymeric coating atop the one or more primer layers.