Abstract:

Corrosion of topside combat systems attachment flanges has been a long-standing fleet problem. The root cause is the need to have a grounded path from the equipment to the hull of the ship in order to minimize Electromagnetic Interference (EMI) that detracts from the proper operation of electronic systems. The problem is exacerbated by the use of different materials for the two faces of the connecting flange, not atypically steel and aluminum that creates a galvanic couple that promotes corrosion as electrons flow from the least noble to the more noble metal. This problem was brought to the attention of the Navy’s Corrosion Control Assistance Teams (CCAT) for remediation. A conductive gasket consisting of an aluminum wire mesh embedded in a polyurethane gel was demonstrated as a solution to the problem. The gaskets are sized according to the flange size and torqued with attachment bolts to affect a tight closure. The wire mesh provides a ground path for EMI protection and the polyurethane gel provides a long-lasting seal that precludes electrochemical action necessary for a corrosion cell. This presentation will provide the results of a two year study jointly funded by the NAVSEA Paint Center of Excellence (PCOE) program and the DoD Corrosion Program Office (CPO) that evaluated the performance of aluminum wire mesh conductive gaskets to include laboratory evaluation, ship demonstrations, and an assessment of the requirements documents for combat system gasket installations.
Outline of the key points to be made
 The flanged connection between topside electronic masts and antennas and the ship’s hull is a corrosion problem
 Efforts to protect this area have been ineffective due to complexity of the process and the difficulty in achieving electrochemical isolation
 Conductive gaskets provide an effective means of isolating the two flange surfaces in a manner that ensures EMI protection while precluding corrosion
 Laboratory testing with salt fog showed that conductive gaskets work for a range of different materials as flange faces
 Ship demonstrations on three ships over a year-long operational cycle showed that the conductive gaskets were effective for corrosion control
 A Commercial Item Description that is currently specified in the governing NAVSEA Standard for Topside EMI controls is being revised to include conductive gaskets.

Conclusions or recommendations
Conductive gaskets provide an effective seal to ensure EMI protection is maintained while precluding corrosion at the interface between an electronic mast or antenna and the hull mount.