1. Corrosion properties of water based and high solids Aerospace coating systems.
IMFAIR th & 11th June 2009
Peter de Bruin Akzo Nobel Aerospace Coatings

2. Content Trends in Aerospace industry because of HSE legislation.
Aerospace substrates, structural and exterior.
Morphology and corrosion of Aluminium.
Corrosion protection of Aluminium.
Developments in Aerospace structural coating systems.
Developments in OEM Aerospace Exterior coating systems.
Comparison Water based versus high solids product.
Aerospace corrosion test methods.
Specifications / corrosion requirements.
Corrosion results Airbus structural coating systems.
Corrosion results Boeing exterior coating systems.
Conclusions.

3. Trends in Aerospace industry because of HSE legislation.
Changes in VOC legislation:
Maximum allowed VOC per product (ready-to-spray).
Primers: max. 350 g./l.
Topcoats: max. 420 g./l.
Limitation of Emission of organic solvents per location.
Reduction / replacement of Cr 6+ compounds.
Chromate free substrate (aluminium) pretreatment.
Chromate free corrosion inhibitors in Aerospace primers.

4. Aerospace substrates, structural and exterior.
Aluminium alloys used in Aircraft construction.
Aluminum alloy
Composition (%)
1100 (Clad layer)
2024 (T3)
7075 (T6) Al
> 99 ~
~ 89.5 Cu
0.12
~ 1.5 Mg
~ 2.5 Mn
~ 0.5 Zn
~ 5.5
Others
~ 1
Tensile strength (psi)
13,000
70,000
83,000
Yield strength (psi)
5,000
50,000
73,000
Elongation (%) 35 18 11

5. Aerospace substrates, structural and exterior.
Other possible substrates, both in construction and for rivets / fasteners are:
Titanium
Lithium Aluminium alloys
Stainless steel
Composite

6. Morphology of aluminum 2024T3
The alloy is inhomogeneous. It contains grains.
Coating
Alloy 1100
Alloy T3
Grain boundaries are sensitive for corrosion!!

7. Morphology of aluminum 2024T3
The surface is inhomogeneous. It contains cathodic and anodic area’s
Ca / cm²; ~ 4.5% of surface area!

8. Filiform corrosion
Thread like corrosion between substrate and coating about 15 µm in depth.
Necessary conditions - Susceptible Al-Alloy. (lit.: % Cu> 0.15% large effect) Al-Mg alloys less sensitive. - Pretreatment. - Damaging of coating. - RH >60% RH. - Initiator; Cl-, SO Presence of O2. - Sufficiently high temperature.