The current way of protecting aluminium alloys used for structural components of aircrafts consists of:
- Using a surface anodizing pre-treatment (hazardous chromated pre-treatment still often used) then spraying either a chromated solvent borne paint or a chromated water based paint. With this process of application, hazardous overspray’s (containing chromates) are important and only 40% in average of the paint is transferred to the surface.
- PPG is the historical leader in electrodeposited paints. We have all the expertise and equipment’s available in that field to design new polymers, formulate anaphoretic paints, characterize surface and interphases, design ecoat lines, educate and assist users.
- PPG is also leading the Aerospace market segment for paints and sealants. We have built a strong experience in chromate free primers for corrosion protection of structural components of aircrafts.
- Based on our experience the use of anodic paint is justified for Aerospace aluminium alloys because a protective anodic layer is formed at the same time the paint deposits at the surface of the alloy during the electrophoresis process. That will allow to eliminate the current hazardous anodizing process step as aluminium alloys used in Aerospace cannot support temperature above 120°C, anodic paint technology only is adapted
- VOC is bellow 100g/l
- Transfer efficiency is very high (98% vs 40% for current paints used for same purpose) so almost no waste
First screening was done by using an existing PPG anodic paint showed encouraging results vs Aerospace main OEMs specifications. In particular critical tests like hydraulic fluid resistance and water resistance were achieved Al2024 alloy without anodizing pre-treatment. Also, first corrosion tests performed on Al2024 were close to the target (3mm max filament). We were strongly convinced that the optimisation of that technology will meet the major OEMs specifications for protecting light alloys like 2xxx, 7xxx and A
This project was designed to help prove anodic Ecoat technology for Aerospace at an industrial pilot scale. Some elements of the background science were examined in order to validate the technology and understand underlying mechanisms.
It has been shown that the electrodeposition process is viable in terms of both the process viability and cost, that high integrity coating are produced which give outstanding levels of performance when compared with other chrome replacement technologies and we believe the work herein has helped establish this process as a strong option for adoption by OEM's and component suppliers
The consortium consisted of PPG Aerospace who are the original developers of this technology and Dassault Aviation who are a potential end user with an interest in being an early adopter. The University of Lille were engaged as a project partner to provide a range of sophisticated surface analytical techniques used for probing the structure of surface layers from which we were able to determine some mechanistic detail and understand the effects of process variables
The main objective of the project was to further develop a promising chromium replacement technology by gaining information on product performance, characterisation of the deposited layers and the effect of process variables. The final stage of the project was to show feasibility of the process on a demonstrator unit that is intermediate in scale between lab experiments and full industrial scale.