The William A. Irvin, Duluth’s floating museum, was expected to spend four weeks in drydock at Fraser Shipyards, but as of Wednesday, the 611-foot ship will enter its fifth week out of the water. Meanwhile, deliberations over what to do to the vessel’s time-corroded hull continue.

The 81-year-old laker is showing its age.

The Irvin had been slated to have its hull sandblasted and repainted at Fraser, but only after the vessel was removed from the water did the full extent of its deterioration emerge. The hull of the ship appears to have been pitted by the same bacterial corrosion that has plagued the port’s submerged steel structures — including seawalls and docks — for years.

Of particular concern are some of the thousands of steel rivets that hold the Irvin’s hull together. A number of these rivets have been compromised to the point where their future integrity has been called into question.

It’s unclear what corrective action, if any, should be taken to address the situation, said Chelly Townsend, executive director of the Duluth Entertainment Convention Center, which owns and manages the Irvin. She noted that the ship had not been taking on any water, despite the corroded rivets.

“So, it was a surprise,” Townsend said. “There’s a possibility we do nothing and that we just watch them, because they can be repaired from the inside if there are any leaks.”

Stray electrical current also is believed to have contributed to the corrosion, and Townsend said the Irvin will be electrically grounded to guard against further effects. She said the Vista Fleet recently had its smaller tourboats outfitted with similar grounding equipment to fight corrosion, too.

Crews at Fraser continue to sandblast and paint sections of the Irvin, although the work was slightly complicated by the discovery of lead in the last paint job, which is believed to date back to 1986, Townsend said.

Townsend said she hopes to learn by the end of the week what additional repairs may be prescribed for the Irvin, as well as the cost.

The DECC will rely on guidance from Chase Dewhirst, manager of marine engineering for AMI Consulting Engineers P.A. Dewhirst declined a request to be interviewed by the News Tribune Tuesday but said he planned to participate in a press conference on the state of the Irvin this week.

The DECC received a $504,000 state historical grant to undertake repairs of the ship, and Townsend said those funds will be supplemented with additional local dollars, if needed.

For the past two tourist seasons, the Irvin has been sidelined, as it had to be relocated from its longtime mooring to allow for a cleanup of contamination in Minnesota Slip, where failing seawalls also required replacement. Consequently, the DECC has been deprived of about $300,000 in annual revenues.

The DECC took advantage of the displacement to address years of deferred maintenance on the ship.

Townsend expressed confidence the Irvin will be back in action soon, welcoming guests aboard by 2020.

She anticipates the rivet problems will prove a modest setback.

“It doesn’t seem like there will be any significant delay. We’re still planning to have it back by the end of September,” she said of the Irvin’s pending return.