For over 20 years at the National Tank Truck Carriers' Cargo Tank Maintenance Seminars, presentations have addressed the perils of corrosion. And yet the issue persists.
According to a 2002 study by the Federal Highway Administration (FHWA) and NACE International, the annual costs of corrosion for over-land hazmat transportation were about $900,000.
Imagine what it is 11 years later.
“Perhaps in past years, we spent too much time in a reactive sense, talking about what happened,” said John Cannon of Walker Group Holdings LLC. “Today, let's turn that around and see if we can coalesce as an industry.”
Cannon said many corrosion events have been preventable. But to understand the issue, the types of corrosion have to be defined:
• Galvanic. “A couple of dissimilar materials and a solution that carries a charge.”
• Crevice. “Occurs between the gasket and flange in an area that’s not able to be cleaned too often.”
• Atmospheric. “Mostly applicable to carbon steel-type applications.”
• Intergranular. “Usually in welded areas.”
“Stainless steel is essentially a low-carbon steel that contains chromium at 10% or more by weight,” he said. “It is this addition of chromium that gives the steel its unique stainless corrosive-resisting properties. The chromium content of the steel allows the formation of a thin, adherent, continuous, and invisible, corrosion-resisting chromium oxide passive film on the steel surface. Stainless steels are corrosion-resisting because of the metal’s ability to form and maintain a thin protective film of chromium oxide. If the chromium oxide is disrupted or destroyed and a contaminant is not imbedded in the surface, the chromium oxide layer will heal itself under oxidizing conditions.
“As long as the film of chromium oxide is maintained, the stainless steel behaves like gold, silver or platinum, or in other words, it has a passive behavior. Stainless steel can also develop active sites if the protective film is destroyed by scratches, nicks, deposits, or contamination by mild steel or non-ferrous inclusions. When scratched, damaged or machined, the protective film is destroyed, exposing the steel to the atmosphere.
“By definition, stainless steel is virtually immune to corrosion. However, stainless steel is subject to severe corrosion attack, including pitting. The most unfortunate thing about stainless steel is its name. After all, if something is stainless, doesn’t it imply that it will not corrode, stain, or discolor? Unfortunately, this is far from the truth, and stainless steel is subject to corrosion.
“What is a pit? Corrosion of a metal surface confined to a point on a small area which takes the form of cavities. The number one type of corrosion in the tank truck industry is pitting corrosion. The reality is that a pit may look harmless from the surface, but as the pit continues to corrode below the surface it will create significant damage.”
How is pitting affecting carriers?
Groendyke Transport’s James See said the company spent $273,417 in 2011 and $359,244 in 2012 to repair pitted trailers—and that doesn’t include lost revenue.
“We haul a lot of latex to Mexico,” he said. “You can’t get tanks cleaned down in Mexico, so it’s guaranteed that the trailer will get to the border and sit there for a few days. And we’ve got to scrape it. If you scrape a trailer, you damage it.
“Many of these trailers were also repeat offenders. They’d been pitted before and repaired before, which made us question the quality of our repairs. If we didn’t catch the quality of repairs, then it was on us. This led us to establish a repair standard for all of our vendors to adhere to.”
Superior Carriers’ Ken Shafer said it cost the company $346,453 in 2011. The company has 1,296 stainless steel tanks in service.
“The average internal barrel repair cost per tank is $267.33, which is low because some tanks have dedicated service and don’t see a lot of pitting,” he said. “This number has been coming down over the last five years, so things we have in place have helped.
“Products must be approved and assigned the proper tank to be transported in by the maintenance department. The proper cleaning method is assigned at that time. These steps are done prior to giving the rate to the customer. In terms of the time the product will be on the tank from loading to delivery to cleaning, product temperature and ambient temperature is a factor. It takes everyone’s involvement: sales, dispatch, maintenance, tank cleaning, drivers.”
What is the industry as a whole doing?
Cannon said a large group of industry stakeholders convened in Wisconsin in June 2012 to discuss corrosion. First, the top 30 causes of corrosion—within the industry—were identified and classified. Then the most promising approaches to prevent corrosion in cargo tanks were recorded. Finally, the group created 10 “categories of opportunity” to proactively deal with the challenge of corrosion: qualification; inspection and testing; loading; transportation; unloading; cleaning; repair; tank spec’ing; storage; and passivation and pickling.
Working toward qualification may include creating and maintaining a Liquid Products Database (LPD).
“Some very large fleets are already using their own database but it’s an enormous task,” Cannon said.”It seems to me that if 50 different carriers each invested in this, there would be a duplicate effort. We think it would have to be hosted by a neutral industry entity, perhaps NTTC. Maybe it could be based on an electronic hazmat table, with columns added for corrosion data, cleaning, etc. It should be available for personal computers and smartphones.
“It’s an ambitious effort. It needs an administrator, programming, licensing of corrosion data from national associations and corrosion engineers, initial and continuing carrier input in order for it to be a success, and it needs occasional testing to be incorporated into the database.”
Cannon separated the presentation attendees into small groups and asked them to discuss the issue. Here are their comments:
• Populate the LPD with “bad actors” first.
• LPD should be hosted by a “neutral” party.
• Cover 3-A criteria, where applicable.
• Mention the use of product temperature indicator labels (to identify unplanned heat application).
• Consider drafting recommended practices for repairs.
• Recommend more noble weld wire for pit repair.
• Start with all carriers supplying a list of “top ten bad actor” chemicals.
• Qualification is the biggest opportunity, followed by cleaning and passivation.
• Make the LPD so good that “carriers cannot operate without it”—which will foster a virtuous cycle of use and improvement.