Ship Corrosion Inspection Standards Developed
A team of engineers at the Corrosion and Coatings Engineering Branch at the U.S. Naval Surface Warfare Center, Carderock Division (Potomac, Maryland) have developed a new standardized method of conducting ship inspections, which is believed to lower current maintenance costs.
According to materials engineer Jamaal Delbridge, the project was inspired by a previous proposal written by Brittany Preston-Baker, another member of the Carderock Division and who is also a part of the Corrosion Control Assistance Team.
The New Standard
In following Preston-Baker’s proposal, during an assisted maintenance procedure, CCAT members noticed that various window structures on ships showed shattering and cracking in the sealants and that other corrosion products were also beginning to deteriorate.
To further understand the corrosion issue, Delbridge inspected 14 ships across the fleet. Ou of the Arleigh Burke-class destroyers, Wasp-class amphibious ships and the Ticonderoga-class cruisers, research showed that destroyers suffered from the most corrosion issues and that window structures in particular showed reoccurring corrosion issues across the board.
As reported by Materials Performance, several factors contributed to the corrosion issues: a corrosive environment as well as an engineering design flaw that enabled entrapment of fresh water and seawater on top the window seal and ineffective repairs, such as painting over sealants and using high-impact tools causing the glass to shatter in some cases.
Research also revealed that the window configurations had dissimilar metals. Delbridge went on to explain the study, saying that, “There were a lot of the corrosion issues. The window frame on the inside was stainless steel, but you had carbon steel nuts and bolts that were connecting the ship superstructure, which is steel. That’s a recipe for galvanic corrosion.”
In the new set of maintenance-requirement cards (MRCs), inspection methods and repairs are explained through step-by-step instructions. One of the developed MRCs recommends annual inspections of exterior steel window-frame structures for corrosion, sealant shrinkage and cracks. Should ship corrosion show more than 10% of a linear area around windows, or if there are issues with the sealant, the second MRC explains proper repair and preservation steps to be taken for the exterior window structure and sealant replacements.
The two MRCs were reportedly developed by Delbridge and Jim Wigle, the CCAT project engineering lead, and have since been uploaded onto a Planned Maintenance System Viewer software—a preexisting document tool that allows users to search, view and print ship-wide maintenance index pages—following its six-month approval process. The new cards are expected to lower maintenance costs by extending the service life of exterior window structures prone to corrosion.
“These windows corrode within six months to a year,” Delbridge explains. “With this new MRC, not only will it give the right procedures, but you’ve extended the service life of these windows. You won’t have to do as much maintenance, which also means decreasing costs.”