Wired (again) on sinking oil tankers:

The New Supertanker Plague

The Erika was neither the first nor the last tanker to succumb unexpectedly to corrosion. Each year from 1995 to 2001, an average of 408 tankers broke apart at sea or barely escaped that fate, according to the International Association of Independent Tanker Owners, known as Intertanko. The leading cause was collision, but nearly as many suffered "structural/technical failures" - often a euphemism in industry circles for excessive corrosion. ...

... In December 2000, the Castor, carrying 8.7 million gallons of unleaded gasoline across the Mediterranean, developed cracks in its deck and had to be drained of its cargo in a risky ship-to-ship maneuver.

Preliminary findings in the Castor case rocked the industry. According to the American Bureau of Shipping, the classification society that certified the vessel, the Castor had fallen prey to "hyper-accelerated corrosion" - swiftly dubbed "super-rust" in the trade press. The ABS downgraded its assessment to "excessive corrosion" in its final report, issued this past October. Nonetheless, that document noted that the vessel's steel had disintegrated at rates of up to 0.71 millimeter a year - more than seven times the "nominal" rate expected by the bureau. ...

... Ever since the Exxon Valdez ran aground in 1989...shipbuilders have focused on constructing tankers that would be impervious to grounding and collision. The solution has been to wrap a second hull around the first; the Oil Pollution Act of 1990 mandates that, by 2015, all tankers operating in the US have double hulls. This innovation has prevented dozens of spills, but it has inadvertently propelled corrosion to unheard-of levels. ...

... Super-rust in aging single-hull vessels can be blamed on an industry in denial. In double hulls, accelerated corrosion is engineered right into the ships themselves. ...

A fascinating tale of technology side effects. In an effort to correct one problem (leaking and vulnerable oil tankers), "solved" by mandating double-hulls, a new problem (super-rust) has been created, leading to who knows what.