Post on 13-Dec-2015
Corrosion properties of water based and high solids Aerospace coating systems.
IMFAIR 09 10th & 11th June 2009
Peter de Bruin Akzo Nobel Aerospace Coatings
2Akzo Nobel Aerospace Coatings
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.
3Akzo Nobel Aerospace Coatings
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.
4Akzo Nobel Aerospace Coatings
Aerospace substrates, structural and exterior.
Aluminum alloy
Composition (%) 1100 (Clad layer) 2024 (T3) 7075 (T6)
Al > 99 ~ 93 - 94.5 ~ 89.5
Cu 0.12 3 - 4.5 ~ 1.5
Mg ~ 1.5 ~ 2.5
Mn ~ 0.5
Zn ~ 5.5
Others ~ 0.5 ~ 1
Tensile strength (psi) 13,000 70,000 83,000
Yield strength (psi) 5,000 50,000 73,000
Elongation (%) 35 18 11
Aluminium alloys used in Aircraft construction.
5Akzo Nobel Aerospace Coatings
Aerospace substrates, structural and exterior.
Other possible substrates, both in construction and for rivets / fasteners are:
Titanium
Lithium Aluminium alloys
Stainless steel
Composite
6Akzo Nobel Aerospace Coatings
Morphology of aluminum 2024T3
- The alloy is inhomogeneous. It contains grains.
Alloy 1100Coating
Alloy 2024 T3
Grain boundaries are sensitive for corrosion!!
7Akzo Nobel Aerospace Coatings
Morphology of aluminum 2024T3
- The surface is inhomogeneous. It contains cathodic and anodic area’s
- Ca 300.000/ cm²; ~ 4.5% of surface area!
8Akzo Nobel Aerospace Coatings
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-, SO4
2-.
- Presence of O2.
- Sufficiently high temperature.