SEATTLE — Closer inspections have been ordered for the two oldest ferries still operating in Washington after corrosion was found over the weekend during Coast Guard checks inside the vessels’ hulls.

The Rhododendron, launched in 1947, and the Evergreen State, which turned 53 this year, can return to service, but Washington State Ferries crews need to prepare them by Friday for tests to determine the thickness of hull steel in corroded areas, said Lt. Cmdr. Todd Howard, chief of vessel inspections for the Coast Guard in Seattle.

That means scraping away paint and corrosion scale inside the hull until workers reach clean steel, Howard said Monday.

“Even though we did find some larger areas in these other two older boats, they are safe to operate on the runs,” Howard said.

Hull-thickness tests also are planned in the coming days for the Walla Walla, built in 1973, the Kittitas (1980), and Cathlamet (1981) after smaller areas of corrosion were found on those boats, Howard said.

“There are bigger areas in the Evergreen State and Rhododendron that need to be cleaned,” he said.

The Coast Guard ordered a dozen ferries inspected after the state’s 80-year-old Steel Electric-class boats, were pulled from service Nov. 20 and retired.

The Steel Electrics had been the oldest ferries operating on salt water in the nation. When repair work was halted on the Quinault, crews had determined that at least 45 percent of the hull needed to be replaced, ferry officials said.

More hull repairs are coming for the state’s aging ferry fleet. On Nov. 30, ferry officials said corrosion “pitting” similar to that found on the Steel Electrics has turned up inside the hull of the Hyak, a ferry built in 1967.

Recent inspections also have determined that hull steel needs to be replaced in some areas on the ferries Kitsap (1980), Chelan (1981), Tillikum (1959) and Spokane (1972). The Klahowya (1958) also needs fresh paint in some areas.

So far, all of the repairs can wait until those vessels are in their next scheduled period of dry dock maintenance and preservation, Howard said.

Two additional ferries, the Yakima (1967) and Kaleetan (1967), also are undergoing inspection.

Gov. Chris Gregoire has asked the Legislature to set aside $100 million to replace the Steel Electrics with three new car ferries. The state also has entered contracts with area shipyards to build three new 144-car ferries.

Reporter Scott north: 425-339-3431 or north@heraldnet.com.