The Navy cruiser USS Port Royal is back in Pearl Harbor shipyard for more than $20 million in repairs — on top of the $40 million spent to fix damage from a 2009 grounding and an $18 million refurbishment immediately before the warship ran aground.

The latest yard period, which began in September and is expected to end in late February, is to address cracks discovered in the aluminum alloy superstructures on all 22 of the Navy’s Ticonderoga-class cruisers, officials said. The ships were commissioned between 1986 and 1994.

The Naval Sea Systems Command in Washington, D.C., said cruiser hulls are made of steel and that superstructures — everything above the main deck — were fabricated using lighter-weight aluminum alloy 5456, a material that has been used by the Navy on deckhouses since 1958.

The superstructures of all the cruisers in the fleet are prone to "sensitization," which contributes to stress-corrosion cracking and worsens with age and heat, said Chris Johnson, a NAVSEA spokesman.

"At this point, all ships in the class are experiencing cracking issues that are related to sensitization," Johnson said in e-mailed answers to Star-Advertiser questions. "There have been various degrees of crack repair on every (cruiser) in the past year."

More than 3,000 cracks have been found on cruisers across the Ticonderoga class, he said. Destroyers and frigates have not experienced the problem, he said.

The Navy has developed a ship repair program to address the superstructure cracks, with some repairs scheduled to be made during a Navy-wide cruiser modernization program.

"However, the Navy continues to accelerate the installation of these ship alterations within budget constraints," Johnson said.

A cruiser Aluminum Superstructure Task Force also was recently established to develop "a more holistic approach" to addressing the problem, he said. Results from the task force are due in mid-fiscal year 2011.

The cracks are not more severe on the Port Royal than on other ships, Johnson said, but were bad enough to warrant the current pierside work.

Commissioned in 1994, the Port Royal is the Navy’s newest cruiser. In August it was in the port of Seattle for Seattle Seafair 2010.

Contracts worth more than $20 million were awarded to surface ship contractor BAE Systems in Honolulu for repairs to the gas turbine intake bulkhead and deck, fuel oil storage tank, superstructure and 06-level cracks, including the replacement of aluminum decking and plating.

Johnson did not directly address whether the corrosion cracks represent a material defect.

The Navy has struggled for decades with the issue of superstructure cracking. In the mid-1970s it changed the temper of the aluminum alloy used for cruisers. That solved some degradation problems, but stress-corrosion cracking continues to occur, Johnson said.

Johnson said the cracks on the Port Royal are not related to the ship’s Feb. 5, 2009, grounding in 14 to 22 feet of shoal water off Honolulu Airport’s reef runway. The 567-foot warship was stuck for four days as wave action rocked the vessel on the reef.

Repairs totaling $40 million included replacement of the Port Royal’s bow-mounted sonar dome; refurbishment of the shafting, running gear and propellers; repainting of the underwater hull; and structural repairs to tanks and superstructure cracks.

When it ran aground, the ship was on its first day of sea trials following an $18 million shipyard refurbishment.

Johnson said the total repair estimate for the cruiser superstructure cracks will not be known until all the ship alterations are completed because each ship has a different repair cost.

The Navy has embarked on a $16.6 billion program to modernize all of its 22 cruisers and 62 Arleigh-Burke destroyers to extend the life of the fleet.

All three cruisers at Pearl Harbor — the Chosin, Lake Erie and Port Royal — will undergo improvements here, along with Pearl’s six destroyers: the Chung-Hoon, Hopper, Paul Hamilton, Russell, O’Kane and Chafee.