Coatings World - August 2010

rosion on high strength aluminum alloys,” said Griffin.

The new technology is not reliant on chrome pretreatments to be effective. AkzoNobel expects the technology to be approved by the U.S. Air Force, under MIL-PRF-32239 in 2010.

AkzoNobel also recently launched the Aerowave series of waterborne structural coatings. The series includes a corrosion inhibiting primer, topcoat and composite primer, all approved by Airbus and all with a VOC content less than 250g/L.

AkzoNobel has launched the Aerodur 3001/3002 basecoat/clearcoat system for commercial aviation, and the Alumigrip basecoat/clearcoat system for general aviation.

“Applications in both OEM and maintenance environments have confirmed that using a basecoat/clearcoat system will reduce process times by 30% when compared to current paint systems used for aircraft exteriors,” said Griffin.

For the general aviation segment, ANAC has launched Alumigrip 4001, recently approved by Cessna, as a dual purpose primer and sanding surfacer, eliminating one whole step in the exterior painting process. This technology is also being tested in Europe by the Norwegian Air Force, Italian Air Force and Airbus.

Sherwin-Williams Aerospace Coatings has introduce a full line of primers that are free of chrome and lead hazards. These priming options meet applicator needs for commercial, military or general aviation aircraft and meet three key requirements—faster priming, protection of the aircraft substrate and providing key environmental benefits.

“We provide the painter a choice in
environmentally supportive primers,
including our latest Chrome Hazard Free
Epoxy Primer, Epoxy Primer Surfacer
and Urethane Primer,” said J. Marc
Taylor, Sherwin-Williams Aerospace
director of sales. “These new low-VOC,
two-component, corrosion-inhibitive pro-
ducts contain no hexavalent chromium
(CR(VI)) and subsequently meet the
Occupational Health and Safety Admin-
istration’s (OSHA) latest standard for
occupation exposure.”
Meeting SAE’s Aerospace Material
Specification 3095 (AMS 3095), Sherwin-
Williams Aerospace Coatings also
launched a two-component Wash Primer
(CM0484646) designed for pretreatment
of aluminum and provides an alternative
pre-treatment option to chemical chro-
mates like Alodine and/or Anodized.

Ultraviolet A (UVA)-curable coatings are being researched as an alternative to traditional two-component (2K) polyurethane aerospace topcoats because of their rapid cure rates, low volatile organic compounds (VOCs), low volatile hazardous air pollutants (VHAPs) and high performance properties.

Bayer MaterialScience LLC and Deft Inc., one of the leading suppliers of coating systems for the aerospace and industrial markets, developed UVA-curable coating formulations that were evaluated against aerospace standards for topcoats. Based on these findings, Todd Williams, industrial post-doctoral researcher, Bayer MaterialScience LLC, presented “Development of UVA-Curable Coatings for Aircraft Topcoats” at the recent Rad Tech UV/EB 2010 Technology Expo and Conference in Baltimore.

Conventional coatings in the aerospace market historically have been based upon 2K polyurethane coatings that require 72 hours to fully develop their physical properties. The development of UVA-curable aerospace coatings is targeted to significantly decrease refurbishing time through greatly reduced curing time.

According to Williams, UVA-curable coating formulations display promising physical properties. A UVA-curable formulation was applied to C-130 and F- 16 aircraft as a stencil coating and was periodically evaluated for color change and gloss retention. After 600 flying hours, the stencil coatings on the C-130 had ΔE values comparable to the conventional polyurethane fluoropolymer coatings.

Aerospace coatings require a compromise of both chemical resistance and flexibility while maintaining hardness. In this study, formulations that yielded such a balance of chemical resistance, flexibility, and hardness were obtained using a combination of hard and soft urethane oligomers and reactive diluents.

“Gloss reduction of these coatings was achieved through a combination of flatteners and oxygen inhibition, leading to flexible, low gloss formulations,” said Williams. “Weathering of UVA aerospace systems is another critical property that can be chiefly controlled by raw material selection.” Through this evaluation, the overall performance of UVA-curable coatings has been shown to rival that of conventional polyurethane coatings.