VISIT THIS SECTION FOR CANADIAN AND USS SHIP WELD ISSUES

 

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Blame it on super-rust, a virulent form of corrosion that has destroyed hundreds of ships and could sink the oil industry.
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On December 7, 1999, the oil tanker Erika set sail from Dunkirk, France, bound for Sicily, carrying 10 million gallons of heavy fuel oil. A few days later, the ship headed south around the coast of Brittany and cruised directly into a powerful storm.

The Erika battled swells of more than 20 feet as it steamed across the Bay of Biscay. Soon the ship began to list, and 11-foot cracks appeared in the deck and hull. The Erika was breaking apart. A helicopter evacuated the crew just before the vessel split in half and sank in 400 feet of water, spreading tarlike petroleum across more than 250 miles of the Loire-Atlantic coastline — Europe’s largest oil spill in two decades.

Built in Japan in 1975, the Erika was typical of today’s older tankers. Sailing under the flag of Malta, it was managed by an Italian operator and chartered by a Bahamian company headquartered in Switzerland. Its Maltese owner was itself owned by two Liberian firms. Deemed seaworthy by Registro Italiano Navale — one of many organizations, known as classification societies, responsible for inspecting and certifying commercial vessels — the Erika had passed every inspection over the year prior to its sinking.

The final report on the disaster, issued in January 2000 by the French investigative agency Bureau d’Enquetes sur les Accidents en Mer, concluded that severe corrosion had weakened the Erika’s hull, causing the ship to flex in the storm and eventually to fracture.

The volume of oil moving by ship is soaring. And in traditional tankers, accelerated corrosion is engineered right into the body of the vessel.

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.

Ships have been corroding since the late 18th century, when wooden hulls were first covered with copper to protect against worms. Mariners have recognized the threat to steel tankers in particular since the 1950s, and classification societies have established a regime of inspections and maintenance to keep corrosion at bay. But the system has failed. Ships that cost hundreds of millions of dollars to build are falling apart on the open sea, endangering the lives of crew members and spilling millions of gallons of oil each year.

For instance, the Nakhodka went down two years before the Erika sank. This 27-year-old tanker broke apart off the coast of Japan, spilling 1.3 million gallons of crude and killing one sailor. The Japanese Ministry of Transport found that portions of the ship’s hull had rusted 20 to 50 percent. 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. (The ABS declined numerous requests for an interview. David Olson, the Colorado School of Mines professor who served as the “independent” metallurgist for the Castor report, also refused to comment.)

Super-rust was initially explained as an unprecedented phenomenon, a highly evolved form of corrosion neither foreseeable nor preventable. The truth is less mysterious: Hyper-accelerated corrosion is the inevitable result when unforgiving chemistry meets the harsh economics and tangled industry politics of transporting fossil fuels.

Rust attacks steel from the moment the metal encounters moisture. To keep that from happening, shipowners paint steel surfaces with corrosion-resistant coatings. The coatings break down with age; conventional maintenance protocols dictate that tankers be recoated periodically. If all this is done properly, a ship should carry cargo for 30 years or so and then retire to the scrap yard without incident.

But first-class ship maintenance has become increasingly rare in recent decades. Since the 1970s — when the Erika, Nakhodka, and Castor were built — profit margins in the tanker business have fallen steadily. Today, tankers change hands two or three times before they’re taken out of service. Temporary owners of second — or third — hand ships tend to be less interested in maintaining their vessels than maximizing the return on their investments. What’s more, the classification societies lack the authority to enforce rigorous standards. These nongovernmental agencies depend for revenue on their clients: shipbuilders, owners, and operators, who can and often do shop their business to competing societies. For instance, the Erika’s owners switched to Registro Italiano Navale after the French agency Bureau Veritas, which had certified the ship for the previous five years, refused to overlook its deterioration. The Erika went down just 18 months later.

So far, super-rust has destroyed only old ships at the end of their useful lives, allowing many in the industry to maintain that the problem is contained. This complacency has become increasingly dangerous in the face of evidence that the latest generation of tankers is even more vulnerable than its predecessors. Ever since the Exxon Valdez ran aground in 1989 — the worst spill in US history, dumping 11 million gallons of crude into Alaska’s Prince William Sound — 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.

Tales of double hulls rusting far more rapidly than expected began to circulate in the early ‘90s, not long after the first such vessels entered the water. The 5-year-old Mobil tanker Eagle, for example, spent almost three months dry-docked in Singapore in 1998, reportedly having her cargo tanks treated for corrosion. According to Seatrends, a leading trade magazine, the Eagle had leaked oil into the space between its inner and outer hulls. (Contacted earlier this year, an ExxonMobil spokesperson repeated the company’s assertion that the ship docked in Singapore for “routine maintenance” and that no leakage had occurred.)

Fearful of government regulation, the shipping world has attempted, as Seatrends editor Ian Middleton put it in a 1999 editorial, to “keep a lid” on such incidents. But inspections keep turning up severe corrosion in new tankers. A 2000 Intertanko report concluded that excessive rust is afflicting double hulls within two years of launch. Without a serious shift in industry practice, it won’t be long before the first double hull goes the way of the Erika.

Rust arises from an intricate subatomic dance in which water’s oxygen and hydrogen atoms snatch electrons from atoms of iron. Because saltwater conducts electricity better than freshwater, the iron in steel oxidizes more quickly in seawater — up to 0.10 millimeter per year, as foreseen in classification-society manuals. Given enough time, this process can eat through even the thickest hull.

The way corrosion attacks the interior of a tanker, however, is more insidious. It can be seen most vividly in the cargo tanks, which line up along the ship’s backbone beneath the deck, and in the ballast tanks that cushion the cargo tanks along their outer edges. In these areas, steel deteriorates at five, ten, even thirty times the nominal rate.

In the ballast tanks, which are normally filled with seawater when the cargo tanks are empty, water conducts electrons between plates on either side, and between separate areas of a single plate — that is, the tanks become huge, if weak, batteries. The increased electrical activity hastens the metal’s degradation. To combat the problem, shipbuilders have traditionally installed bars of reactive metal like zinc or aluminum inside the tanks. The added metal becomes a “sacrificial anode,” which corrodes in place of the ship’s steel. Known as cathodic protection, this method has become less popular as paint manufacturers have developed rust-resistant coatings over the past 20 years or so. In the absence of cathodic protection, however, corrosion sets in when coatings break down. Shoddy repairs can also play a role. In the Castor, corroded plates discovered during inspections were replaced with new plates of uncoated steel, turning the uncoated metal into a sacrificial anode. Thus, the patches rusted even faster than the original metal had.

The processes that drive ballast-tank corrosion hasten the familiar action of oxidation. What happens in cargo tanks, on the other hand, involves more ruinous chemical and biological forces.

At the top of the cargo tanks, the vapor space between the oil’s surface and the underside of the deck traps highly acidic gases — products of the reaction between petroleum, oxygen, and water — that condense against the metal. The deck flexes at sea, causing degraded steel to flake off the ceilings of the tanks, exposing more bare steel for the acid to attack. Examining this area isn’t easy. Scaffolding must be constructed inside empty, unlit tanks, and even then inspectors can view only small portions up-close.

At the bottoms of the tanks, in the water that settles under the oil, corrosive bacteria thrive. Consuming hydrocarbons, microbes like Desulfovibrio desulferican produce acids that dissolve the tanks’ floors and lower sides at rates as high as 2 millimeters per year. Some microorganisms even feed on the coatings that protect the tanks from rust. Essentially, a tanker is a gigantic floating petri dish for a peculiarly vicious sort of steel-eating sludge — the ultimate metallivore.

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. The extra layer of steel gives rust many more square feet of surface area to attack, much of it hidden in cramped, inaccessible crawl spaces. What’s more, these crawl spaces form an insulating layer that keeps the internal temperature much higher than it would be in a single-hull tanker. Corrosion rates tend to double with each 20-degree Fahrenheit increase.

At the same time, manufacturing efficiencies have reduced the thickness of hulls and decks. Guided by software modeling, designers put plenty of steel where it’s needed for strength, while reducing it in the rest of the structure. The advent of high-tensile steel — stronger than conventional steel but no more rustproof — has allowed naval architects to further pare the metal structure.

These developments have led many shipbuilders to trade corrosion-resistance for lower cost. Every ounce of steel saved in the construction of a new ship translates into greater profits for the builder and reduced fuel bills for the owner. Between 1970 and 1990, the amount of steel used to construct a tanker declined by almost one-fifth, according to Tankers Full of Trouble, a 1994 book by Eric Nalder based on his Pulitzer Prize-winning Seattle Times series. Modern tanker walls are only 14 to 16 millimeters thick, compared with 25 millimeters a generation ago. Assuming a microbial corrosion rate of 1.5 millimeters a year, rusted-out pits would reach halfway through those hulls in five years.

Even without a spill, the consequences of an internal breach leaking oil into a double hull could be catastrophic. Asked what might result, shipbuilding consultant Rong Huang gives a one-word answer: “Explosion.”

All ships look old unless they’re freshly painted. At the Avondale Shipyard, upriver from New Orleans, the only unblemished metal surfaces are rails that support rolling dockside cranes and the gleaming blue sides of the state-of-the-art tanker Polar Resolution. Every other steel surface in the yard is dusted with flash rust, a ruddy patina that appears almost as soon as the steel is exposed to air. This superficial oxidation is sandblasted away before the metal is painted and coated.

Some surfaces, however, never get coated at all. These unprotected areas invite the risk of destruction from within.

Contracted by Polar Tankers, a division of Phillips Petroleum, the Polar Resolution is one of four $230 million ships designed for the iceberg and reef-strewn run from Valdez, Alaska, to Puget Sound. The 895-foot vessel has not only a two-layer hull but duplicate engine rooms, navigation systems, and propellers. Its 12 cargo tanks hold 42 million gallons of oil. When its sister ship, Polar Endeavor, set sail last spring, Professional Mariner magazine named it Ship of the Year.

A series of ladders and stairways descends steeply to the floor of the Polar Resolution’s empty cargo tank number five. The walls rise 100 feet to the main deck. A band of light streams from the hatch high above. From the inside, the tank is like a vast steel cathedral, a shrine to man’s thirst for oil.

The tank floor is covered with epoxy. But overhead, the vapor space is uncoated — contrary to classification-society recommendations.

This expanse of bare metal is a stark emblem of the industry’s failure to face up to the hazard of corrosion. With each disaster or near-disaster, authorities have launched an investigation. When corrosion has been implicated, the result has been a litany of recommendations that hardly varies from year to year: Coat the vulnerable surfaces of the ballast and cargo tanks, inspect them frequently, and remove substandard tankers from service. But these guidelines are honored mostly in the breach. According to the ABS report on the Castor, the ship’s last inspections “failed to adequately represent the condition of the vessel’s structure.” In other words, the investigators missed the damage.

Supertankers are the biggest moving structures ever built, yet the system for constructing, inspecting, and certifying them is a relic of the 19th century. At one time, the classification societies were adjuncts to the marine insurance business. Today, they call themselves the self-regulating arm of the shipping world; the avowed mission of the ABS, for instance, is “to serve the public interest as well as the needs of our clients by promoting the security of life, property, and the natural environment.” In practice, the societies serve the shipowners. The leading organizations, which include the ABS, Lloyd’s Register in London, and Det Norske Veritas of Norway, are staffed by conscientious experts, but they work within a system where no one is answerable for the condition of the ships. There is no FAA for tankers.

What’s more, the tanker industry is overrun with so many holding companies, limited-liability partnerships, and owners-of-record that even determining who bears ultimate responsibility for a ship can be difficult. Authorities investigating the Erika found the owner’s capital structure so opaque that it was nearly impossible to figure out who controlled the company. Following the inquiry, Paul Slater, chair of shipping conglomerate First International Group and a member of Intertanko’s Communications Committee, declared the current inspection system “monstrously outdated.”

Given the industry’s reluctance to change, the solution may lie in a new shipbuilding material that’s not only impact-resistant but effectively rustproof. In fact, such a material already exists. A pair of Canadian brothers, Stephen and Michael Kennedy, have come up with a steel-and-plastic composite that’s cheaper, stronger, and more durable than steel alone. The Kennedys’ technology, according to authorities quoted in Marine Bulletin, published by Lloyd’s Register, “has the potential to change the face of shipbuilding.”

On Christmas Day 1995, Michael Kennedy, a civil engineer turned entrepreneur, was chatting with his structural engineer brother Stephen in their mother’s Ottawa kitchen.

“I asked him what he was working on,” Michael recalls. “He told me about this process where you inject plastic between steel plates.”

Michael asked what the possible applications might be. “Icebreakers,” his brother replied.

How many of those are built every year? “The answer was, not very many,” Michael says. “So I asked, ‘How many ships get built in a year overall?’” Hundreds, Stephen surmised.

On the lookout for his next venture, Michael realized that he had found it. After a few years of groundwork, the pair launched Intelligent Engineering to market their composite Sandwich Plating System. Tim, their younger brother, also an engineer, joined the firm in 2000.

In person, Michael and Stephen Kennedy seem like perfect complements. Michael, 48, is the blunt yet personable businessman. Stephen, 45, is the professorial, slightly inward scientist. With a lab in Munich (a joint project with German chemical giant BASF) and offices in London, Ottawa, Oslo, and the Channel Islands, they’re determined to change the way ships are built.

Engineers have long understood the benefits of sandwiching a lightweight core inside a stronger outer shell. Honeycomb materials encased in steel are common in airliners, for instance. Stephen Kennedy’s accomplishment was to develop a composite plate that could be incorporated into large weight-bearing structures, and that could be manufactured and assembled economically.

“I was working on offshore structures in the Beaufort Sea in 1984,” off the coast of northern Alaska, Stephen recalls, “trying to make them impact-resistant. As a structural engineer, you use concrete and steel. It became clear to me that those are just the wrong goddamn materials.” A steel-and-plastic sandwich, he realized, would have the characteristics he was looking for.

Working closely with BASF, it took Stephen years to come up with a plastic with the right combination of strength, density, and ductility, the ability to stretch without breaking. Eventually, he narrowed his focus to a class of polyurethanes known as elastomers, and by 1996, he had developed a technique for injecting the material between two sheets of steel. The process was cheap, only a few cents per kilogram of SPS, and the elastomer set within 15 minutes. The resulting plate was as strong as steel reinforced by welded-on metal stiffeners, yet it weighed 20 percent less.

To date, the technique has been used to repair several car ferries in Europe: A second layer of steel is bonded to an existing plate with elastomer in between. In March, a Canadian Coast Guard icebreaker received this treatment. The company’s first “newbuild” will be a 320-foot barge on the Rhine River, to be completed this year. The ultimate goal is an SPS tanker.

The advantages of SPS for a ship’s hull are readily apparent. Under extreme stress, the surface gives without giving way — unlike steel plating, which tends to shear like paper. By drastically reducing the number of stiffeners required to build a ship, SPS cuts the number of welds in half, eliminating thousands of failure points prone to degradation. The simpler structure makes an SPS ship easier to maintain, allowing it to spend less time in dry dock and increasing its service life. The vessel weighs less and burns less fuel. And, of course, plastic doesn’t rust.

Intelligent Engineering has enough money in the bank to cover the next three years. After that, the company’s future depends on its ability to penetrate the insular world of big shipbuilders. Though they’re loath to criticize potential customers, the Kennedys are under no illusion that shipyards are fertile ground for innovation.

“Shipbuilders have hundreds of years of experience and 100 years of building steel ships,” Michael notes. “They’ve learned empirically what works and what doesn’t, and they’re very reluctant to change.”

“It’s hard to get to know people in the industry, and it’s very conservative,” Stephen adds. “If they’re not forced into making changes, they won’t change.”

About 3,000 tankers carry petroleum products worldwide. More than half were built before 1990, and almost 700 of those are more than two decades old — each a potential Erika in the making. Then there are the 640 double-hull tankers that went into service between 1998 and 2001; a dozen or so leave the shipyard every month.

The construction boom of the late ‘90s has led to an oversupply of ships and a consequent downward spiral in shipping rates, intensified by stagnant oil prices. Margins in the oil-transport business are as low as they’ve ever been, making the cost associated with reform and improved ship maintenance even more burdensome.

“A huge number of double-hull vessels will come of age at the same time,” warns Basil Papachristidis, chair of the Hellespont Group, a tanker owner and critic of current shipbuilding standards. “We’ll probably see accidents like the Erika, except on a much larger scale.”

In many ways, today’s tanker industry resembles the passenger-liner business before 1912 — the year of the Titanic. Then, as now, there had been a burst of shipbuilding powered by rapid advances in marine engineering technology. Competition among the dozen or so leading passenger lines was fierce. Safety and structural integrity were often sacrificed for speed and spaciousness: The Titanic’s bulkheads, for instance, rose only 10 feet above the waterline as opposed to 30 feet in older, more robust vessels. According to “Risk Management and the Titanic,” an essay by Canadian structural engineer Roy Brander, “The owners and operators of steamships had for five decades taken larger and larger risks to save money — risks to which they had methodically blinded themselves.”

That’s a perfectly apt description of the tanker industry circa 2002. Many experts downplay the threat of super-rust to double-hull tankers — but when pressed, they acknowledge that they can’t refute that tankers now at sea are in danger. “No inspection is perfect” is a common refrain. Another disaster on the scale of the Exxon Valdez may be the only thing that will force overly cost-conscious builders and owners to shed their blinders.

The Erika has been drained of its remaining oil and left on the ocean floor, the Castor sold for scrap and towed to a beach in India to be turned into less monumental products like concrete rebar. European authorities have joined the US in banning single-hull tankers by 2015. Meanwhile, the volume of oil moved by ship is soaring. Tanker traffic around the globe will nearly double by 2020, according to the US Energy Information Administration.

In early 2000, the International Association of Classification Societies reported that four of Erika’s sister ships had suffered severe structural failure. Periodic inspections of one, the Green King, had revealed extensive underdeck corrosion repeatedly throughout the ‘90s. The ship’s owners switched its flag from Malta to Liberia in 1996. Later, they changed its name. The tanker is still sailing today.

 

 

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Contributing editor Richard Martin (rbm80_tis@yahoo.com) wrote about Big Steel in Wired 10.02.