Soft coatings can hide deadly corrosion

LONG BEACH, CA - When I stopped by to visit TMT Services at their facility here recently, own Michael Nahm produced a glass jar containing a vile looking gelatinous goo.

"Here, smell this." Unscrewing the lid he gleefully shoved the jar under my nose. "This is soft coating."

I fell back reflexively, cringing at the stench. Michael laughed. "Pretty harsh, isn't it? Imagine anyone trying to inspect a ballast tank coated with this stuff."

Ballast tanks are the marine industry's dirty little secret. They're dark, cramped -sometimes crisscrossed with structural members. To adjust a vessel's center of gravity, trim or draft - to displace other loads and keep the vessel level - they're drained and flooded regularly with seawater. And they're made of steel.

Paraphrasing from The American Bureau of Shipping (ABS) Rules for Building and Classing Steel Vessels, first published in 1890. In an electrolyte of seawater, there is nothing to retard the dissolution of untreated steel.

It's called corrosion -- the process by which a metal reacts with its environment to form an oxide, a compound similar to the ore from which it originated. As a consequence of the second law of thermodynamics, steel will return to its stable, oxidized, low-energy state as quickly as environmental conditions allow.

Rust never sleeps.

Though hardly a new problem, corrosion has emerged more recently as a focus of international concern to the shipping industry. Oceangoing vessels have vanished mysteriously at sea and a major suspect appears to be hidden corrosion.

The US Coast Guard, classification societies and insurance companies like Lloyd's are now paying very close attention to protective coatings used in ballast tanks.

Like most things in life, corrosion protection presents a range of choices. Hard coatings are expensive to apply, require careful surface preparation, and last for many years. Semihard coatings are quicker, cheaper, but don't last as long.

Then there are soft coatings. Soft coatings are inexpensive, easily applied fat-based products. Hardly any surface preparation and no solvents are required. For the cost, soft coatings afford comparatively good protection. They inhibit, but do not stop corrosion. It is estimated that about 40% of all tonnage in the world has soft coatings in the ballast tanks.

Bert A.M. Kok has gained some insight into this arena during his 30 years of experience as a corrosion consultant with his company B.K. Associates, BV, the Netherlands.

"Soft coatings are popular for ship owners who want to hide the lousy steel conditions. This is called wallpapering. It was also a popular choice for those characters who wanted to sell their vessel. With that grease in there, nobody would go through the ballast tanks," Kok says.

"Nowadays, anyone intending to buy a vessel will check the steel condition of the ballast tanks first. It is cheaper to replace the main engine than to reblast and recoat the ballast tanks."

The problem is implied by the name. Soft coatings stay soft. They wear off at low mechanical impact, even from water movement. Some amount of soft coating is discharged each time ballast tanks are emptied. Now, because they are classified as a chemical waste, specialized treatment is required for their disposal. There is also the further serious downside of potential loss of life and/or capitol investment.

"The inspection in ballast tanks had to be executed more rigorously by the surveyors," continues Kok. "But haw can one rate the status of steel when it has been covered with grease-like products?

"One has to wipe the grease away before one can see. Surveyors have been refusing inspections because of hazardous conditions."

As of this year, ABS has new, more stringent rules for ballast tank inspections, requiring soft coating, removal from ballast tanks to facilitate inspections, now required to be annual. Ballast tanks with hard coatings must now be inspected every five years.

Soft coatings removal, while mandatory, is a potentially miserable, time-consuming, and costly undertaking The reaction of Dan Moylan, port engineer in charge of maintenance and repairs for shipping vessel fleet operator Sea-Land based in Long Beach, is described by Michael Nahm.

"He didn't even think I'd show up." Descending into the Sea- Land Discovery's forepeak ballast tanks and successfully removing soft coatings so that the steel condition could be inspected and repaired was the biggest challenge of Nahm's new career as owner of RUSTECO, manufacturer of GreaseMaster.

"Stopping a vessel during its operation in port costs a lot of money. This is the reason why the world is looking for solutions to remove the grease (soft coatings) and install a (new) hard coating," Kok concludes.

Nahm believes he's got one of the few solutions available anywhere.