Corrosion issues on a Collins-class submarine will mean two subs will be docked at Osborne shipyards for first time since 2011-12

Plans to return one of Australia’s Adelaide-built Collins-class submarines to service have hit a seven-month delay.

Serious corrosion issues on one of Australia’s Collins Class submarines will mean two subs will be docked together at ASC’s Osborne shipyards for the first time in more than a decade.

The delay to the works program will put three of the navy’s six-submarine fleet out of the water for at least the next five months.

ASC chief executive and managing director Stuart Whiley said were currently two boats in for docking – Sheean at Osborne and Farncomb in Western Australia – with a third, Rankin, to be taken into Osborne in coming weeks.

The earliest due for completion is Farncomb, which has also had corrosion issues and will be handed back to the navy in October.

HMAS Sheean has serious corrosion issues with the weapons discharge system and some hull forgings. Picture: LSIS Leo Baumgartner/Australian Defence Force via Getty Images

Sheean had been due to be released back into operation “now, effectively”, but Mr Whiley said the extended work meant the boat would be sidelined until the end of the year.

“We’ve had corrosion issues with the weapons discharge system and also some hull forgings,” he told a Senate Estimates hearing in Canberra on Friday.

Mr Whiley said such corrosion issues had not been seen before, and the affected parts needed to be removed and replaced.

Under questioning from SA Liberal Senator Simon Birmingham, he said there had not been two submarines docked at Osborne at the same time since 2011-12.

It is also the first time since 2012 that half of the Collins Class submarine fleet will be out of action.

Asked whether the delay had been brought to her attention, Finance Minister Katy Gallagher said “no it hasn’t, but it would not normally be, I wouldn’t have thought – it would come through defence”.

Senator Birmingham said the comments of Senator Gallagher, the minister responsible for ASC, reflected “an appalling lack of urgency and disinterest in the availability of our critical defence assets”.

“New problems in Collins and delays in availability should be sending alarm bells through the Albanese government but instead they’re just shrugging their shoulders,” he said.

“The government must get on top of these delays so as not to endanger the Collins Life of Type Extension (LOTE) program and ensure continuity of submarine capability prior to AUKUS deliveries of nuclear-powered submarines.”

A Defence spokeswoman said sustainment of the Collins Class submarines continues to meet the navy’s operational requirements.

“Defence works collaboratively with its submarine enterprise partners to proactively manage the Collins Class sustainment schedule, including prioritising work in order to steward our submarine capability,” she said.

“Treatment of corrosion is routine and an expected part of Collins Class submarine sustainment.

“The government is committed to extending the service life of the Collins Class submarines starting with the life-of-type extension of HMAS Farncomb, which will commence in 2026.”