The electrocoat system is an environmentally-friendly aqueous painting process with a long history in the automotive and industrial sectors. Recent research advances in lowering the cure temperature and incorporation of non-chromated corrosion inhibitors has made the use of electrocoat practical for aerospace applications. Electrodeposited primers are environmentally friendly coating technologies widely used in the automotive, industrial, and structural commercial markets. The combination of the non-chromate pretreatment with the chromate-free electrocoat primer offers an environmentally friendly alternative to conventional hexavalent chromate-based spray application methods while maintaining acceptable corrosion and adhesion performance. 

Naval Air Systems Command, U.S. Air Force, U.S. Coast Guard and PPG was awarded the ESTCP program, WP-201010. Through this program a joint testing protocol was completed and a demonstration/validation (Dem/Val) program was established and successfully executed. The Dem/Val had five years of operational performance on multiple aircraft and will continue to be monitored after the completion of the ESTCP program.

Technology Description

The electrodeposition process first requires that the parts be electrically conductive. Parts are initially cleaned and pretreated with treatments such as conversion coating or anodizing to prepare the part for electrocoating. Parts are dipped into a coating bath where direct current is applied between the parts and a “counter” electrode. In the case of anionic electrocoat chemistry, the primer is negatively charged and the part is positively charged. The coating is attracted by the electric field to the part and is deposited onto the part. Parts are removed from the bath, rinsed to reclaim undeposited solids, and then baked to thermally cure the deposited material. 

Demonstration Results

The performance assessment for the Field Service Evaluation was conducted on four aircraft, three KC-135 aircraft and one E-3 aircraft. Detailing information for the cost assessment is ultimately based upon a location by location assessment.  For purpose of this program, Tinker Air Force Base was the focus of the cost assessment but the rationale and modeling can be employed for other locations. The Electrocoat system is expected to result in significant cost and environmental benefits relative to the baseline materials and processes. 

Implementation Issues

Implementing a new coating technology in the military is challenging; especially a new coating technology that also requires new application equipment. The initial target for anodic electrocoat primers was the Air Force for use on aviation assets. However, simply convincing the system program offices is not sufficient. Another critical audience to on-board is the process engineering team at each Air Logistics Center (ALC) who manage coatings processes. While a new coating technology may provide excellent performance, the process engineers need to be confident that the new process is adoptable in the ALC without negatively impacting existing operations.