Depot-level Department of Defense (DoD) corrosion prevention and control operations are critical to maintaining the readiness and operational service life of air- and land-based weapon systems and support equipment. The corrosion protection afforded by any coating system, whether applied to the surfaces of ferrous or nonferrous metals, is dependent on the quality of pre-paint cleaning operations. Accurate real-time assessments of cleaning efficiency for large-area surfaces are difficult to measure and require the judgment of experienced production personnel. Areas that are inadequately cleaned will lead to end-of-process rejections, unnecessary reworking, and in-service coating failures. As a result, there is a tendency to overclean a soiled area to reduce the frequency of problems associated with undercleaning. Overcleaning consumes production time and capacity, slows subsequent maintenance operations, and increases processing costs and waste stream volume. Critical cleaning operations already have analytical support to determine cleanliness, but these methods are too expensive, slow, and cumbersome for widespread use. The objectives of this project were to verify the effectiveness of visual cleaning performance indicators (VCPI) for large-area cleaning operations, quantify the costs and benefits, and transition the technology to depot-level maintenance facilities.

With VCPI, which was developed under SERDP project WP-1117, classes of contaminants are labeled early in the cleaning process with trace amounts of a safe, environmentally acceptable commercial dye. The labeled areas identify locations where additional cleaning is needed. The cleaning process continues until all traces of the colored dye and the contaminant are removed. In this way, the VCPI system helps determine sufficient cleaning of contaminated surfaces. VCPI is useful for a broad range of DoD cleaning needs. This demonstration and validation (dem/val) effort was performed by a joint Air Force, Navy, and Battelle Memorial Institute team and focused on contaminants encountered during large-area aircraft and ship cleaning operations.

This project was considered a partial success from the standpoint that the respective dem/val tests validated the results obtained during the laboratory- and field-based studies. Specifically, the selected VCPI dye solutions were (1) easily prepared in the concentrations required to quickly label the varying degrees of contamination on large-area surfaces and (2) able to be efficiently spray dispersed onto the targeted structures identified by the Air Force and Navy representatives. The VCPI dye solutions visually labeled hydrophobic soils (i.e., greases and oils) on the underside surfaces of a single A-10 aircraft at Hill AFB, as well as soluble salt residues on the painted forward hull surfaces of the USS Halyburton at Mayport Naval Station. The resonance time for the dyes on the surfaces was minimal, the visual detection limits were optimal for the conditions within the respective dem/val environments, and the dye/contaminant removal rates were acceptable for the surfaces being investigated.

Certain process-related failures encountered during the dem/val tests that potentially may limit the acceptance of the VCPI technology in a large- area surface cleaning operation include the dye staining of support equipment, adjacent structures, personal protective equipment, and surrounding infrastructure. The time and personnel required to protectively mask and/or clean up the surfaces of these non-targeted structures offsets any savings associated with the time, manpower, and materials savings proposed from the use of the VCPI technology. Finally, the costs associated with containing the VCPI dye solutions used for pier-side Navy ship applications also represent a negative factor (economic and environmental) in the DoD acceptance of the VCPI technology.