The pressure hull of a submarine has many penetrations to allow for the ingress and egress of sea water, fuel, lube oil and air. For the Collins Class submarines, specifically designed steel hull forgings are installed in the hull to provide reinforcement for these penetrations. This paper presents a case study of corrosion and repair of the hull forgings.

The original nickel plated design of the hull forgings suffered corrosion due to sea water attack and subsequent dissimilar metal coupling. The corrosion resulted in metal loss which introduced a risk of serious impact on the function of the forgings. Short-term repair of the forgings was implemented by way of localized weld repair and selective brush plating of nickel. Simultaneously, investigations into long term solutions were carried out.

The preferred solution for long term corrosion protection was to clad weld the bore and flanges of the hull forgings with Alloy UNS N06625. Qualification for welding the intricate shape of the forgings was conducted and corrosion trials completed. The solution was implemented and has been successful. The cost of the solution was significant but the benefit of assuring hull integrity and submariner safety justified the expense.

Subject
Nickel coatings, Test methods, Water, Materials, Valves, Welding, Inspection, Flanges, Waterline, Hull, Penetration, Repair, Nickel
Keywords:
nickel corrosion, nickel plating, UNS N06625, clad welding, submarine, forging, corrosion prevention
Government work published by the Association for Materials Protection and Performance (AMPP) with permission of the author(s). Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2008
GOV
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