Test and Evaluation of Corrosion-Mitigating Covers
Authors: Patrick Cassidy, Elzly Technology Corp (presenting); John Wegand, U.S. Naval Research Lab; Paul Slebodnick, U.S. Naval Research Lab
The U.S. Navy is investigating methods to lengthen the service life of exposed topside systems and reduce requisite maintenance hours. Research performed by the U.S. Air Force shows that sheltering equipment from rain and salt fall can significantly decrease the corrosion rate and material loss of bare steel components. Currently, the Navy accomplishes this by using fabric cover materials to shelter various assets on ship topsides. Traditionally, military specification materials made from vinyl reinforced fabrics have been used, but advanced technology cover materials are quickly becoming available as alternatives.
This program was set up to evaluate performance of the legacy cover materials and the advanced cover materials versus use of no cover. Various properties of the advanced cover materials were tested in order to make comparisons with the current military specifications. The Navy plans to use this data to create a military specification to govern the procurement and use of these new advanced cover materials. The properties tested for each cover material were: Corrosion Mitigation, Breaking Strength, Tearing Strength, Abrasion Resistance, Ease of Use (fitted design), Drying Time, Wet/Dry Weight, Ultraviolet Degradation and Moisture Vapor Transmission Rate. Further, relative cost for each cover material was also assessed.
After conducting multiple rounds of testing, the program determined that the significant factors affecting corrosion of bare steel coupons protected by covers was whether the coupon was protected by a cover or not and where it was located (environment). There was no significant difference in corrosion performance among different cover material types (excepting a legacy non mil-spec canvas material). Inclusion of multiple layers, inhibitors and wicking layers did not provide any substantial benefit to controlling corrosion versus a common Navy vinyl material. Based on these findings, it is recommended that cover materials be chosen for the other properties they possess that will suit the required service environment/application. Cover material cost, ease of use (weight, dry time, being fitted, etc.), and the mechanical properties should be the highest priorities when making a procurement selection.