By Guy Span, S.D.

In 1999, Nichols Brothers Boatyard built a new Incat design, Jet Cat Express for Catalina Island service (this should not be confused with the Jet Cat Express that operated for Vallejo). Shortly after entering service, mysterious hull cracking and pitting developed. Nichols replaced a shaft bearing, believing that the problem might have been caused by excessive vibration. Despite that, the problems grew.

Because this was a passenger vessel, the U.S. Coast Guard was consulted and they performed metallurgical tests. They concluded that the aluminum plate supplied by Alcan was a type (H321) not suitable for marine applications. By the time they had reached this conclusion, some 750,000 tons of this plate had been delivered to Pacific Northwest boatyards, including Nichols.

In turn, bits of this plate had been installed in about 300 vessels. Some of this was in very small vessels or in non-sensitive areas (such as superstructure). Some was in more sensitive hull areas of the Bay Area’s new high-speed vessels, including Golden Gate’s Mendocino and Alameda –Oakland’s Peralta. Essentially, installation of this plate in hull areas leads to rapid corrosion and possible integrity failure.

So how could this happen? There are no short answers. According to the U.S. Coast Guard and the aluminum suppliers, the problem developed because H321 was supplied by Alcan from its Kingston, Ontario mill and the manufacturer stated that this product was a non-marine grade. Matt Nichols (of Nichols Brothers) finds this statement interesting because his receipts for aluminum come from an Oswego, NY mill.

In the past, heat-treated H321 was a standard marine application. Apparently, the Oswego mill changed from heat-treated aluminum to a cold rolled process. Speculation is that the magnesium in a cold rolled sheet fails to be evenly absorbed, leaving pockets susceptible to corrosion. Nichols noticed that where they had heat-treated the plates at the welding joint, no problems occurred. The problems developed instead nearer the center of the plate, a further indictment of the cold rolling process.

Despite the fact that the aluminum suppliers have the wrong story, Matt Nichols called the Alcoa representatives "stand-up people all the way." In short, Alcoa has funded the replacement of defective plates and even the rent of replacement vessels, while the work is being performed. And in some cases, the work is not cheap. For the Peralta, the superstructure is going to be lifted off the old hull and placed on a newly constructed one. The Mendocino repair effectively involved building a complete new ferry.