Corrosion Buster Symet Shines in Tank Lining Business >By Foss Farrar

Feb. 1, 1999
SYMET Inc, a custom coating applicator in Milwaukee, Wisconsin, entered the tank trailer lining business in 1995 as an off-shoot to its established work

SYMET Inc, a custom coating applicator in Milwaukee, Wisconsin, entered the tank trailer lining business in 1995 as an off-shoot to its established work in other industries. Tank trailer work now accounts for up to 20% of the company's overall business.

"The percentage of any segment of our business varies widely," says Tim Ash, president of Symet, which was incorporated in 1981. "We do a lot of work for repeat customers, and how much we do for any particular business depends on the needs of our customers."

Besides tank trailer linings, Symet applies protective paint and coatings to tanks used for chemical storage and water treatment, as well as to structural steel, weldments, piping, and exhaust and duct fans.

Symet has plenty of room to work on tank trailers. The company's 36,000-sq-ft plant in Milwaukee has a 10,000-cu-ft paint-blasting booth, a 36,000-lb-capacity forklift, and two traveling overhead cranes. Trailers enter the plant through a 15-ft-high front door that is 18 feet wide. Inside working height (from floor to bottom of crane hook) is 21 feet.

In late 1994, Montgomery Tank Lines, based in Plant City, Florida, was researching specific tanker linings that could help prevent tank corrosion caused by hauling specific commodities. Montgomery Tank contacted Plasite Protective Coatings, a coatings manufacturer in Green Bay, Wiscon-sin. Plasite, a supplier of coatings to Symet, recommended Symet as a qualified applicator of its products. In 1995, Symet lined its first tank trailer for Montgomery Tank Lines. The trailer was lined with a Teflon-filled epoxy.

Symet now is well established as a lining applicator in the tank truck industry and is an associate member of the National Tank Truck Carriers Inc (NTTC).

"Most of our tank trailer work is lining new trailers," Ash says. "We can apply linings to aluminum, steel, or stainless steel trailers. Besides new applications, we can remove linings and reapply new coatings in older trailers. We also repair damaged linings if the damage is limited to the lining system."

Symet focuses on the application of sprayed-on coatings. Symet is an applicator of various coatings, including vinyl ester, baked phenolic, baked epoxy, epoxy phenolic, alkyd systems, polyamide epoxy, coal tar, and polyurethane. Lining selection is left to the tank truck customer working with a coating manufacturer. For example, Symet may send the customer to Plasite for coating selection.

"The coating manufacturer will test the product to be hauled in the tank trailer to determine whether a particular lining is resistant to that commodity," Ash says. "The manufacturer tests to see if the lining provides the resistance necessary to prevent corrosion, or the release quality sought by the carrier."

Some linings in tank trailers are applied to allow commodities to flow out of the trailers easier, Ash notes. For instance, Symet has lined aluminum trailers with Plasite Number 9145 TFE, a Teflon-filled epoxy, for this purpose.

Choosing the proper coating for a particular tanker application can be tricky, Ash says. Getting the job done right is a joint effort involving the shipper, carrier, coating manufacturer, and applicator.

"Many of our customers are hauling proprietary chemicals," Ash says. "But they have to describe the chemical composition of the cargo to the coating supplier so that tests can be performed. And the coating manufacturer has to agree to keep the composition of the chemicals confidential."

One critical factor sometimes overlooked in choosing a lining is the temperature at which the chemical is transported, he adds. Some chemicals that are mild at lower temperatures become corrosive at high temperatures.

Tank trucks generally get two to four coats of the lining substance. Coatings are spray-applied to a film thickness that can range from 5 mils to 60 mils, depending on the type of protective systems required.

The first step in applying a coating is to ensure that the tank is not contaminated. Tank trailers that have been in service must be pressure-washed. Then the tank is sandblasted and vacuum-cleaned.

Next, the application material is brushed on all weld and wedge edges on the surface of the tank. After this job is completed, the tanker is ready for the first coat. About 24 hours later, a second coat is applied.

"Phenolic linings require intermediate curing between each coat application at a metal temperature between 200 to 250 Fahrenheit and a final bake at 350 to 400 F," Ash says. "Some coatings require a heat cure after the final coat. This helps drive out all of the solvents. Polymerization of epoxies is achieved by introducing heat after the coating is applied."

Symet follows Occupational Safety and Health Administration regulations in its coating-application procedures. Applicators use Binks HVLP or Graco airless equipment to apply the coatings. They wear DuPont Tyvek coveralls and full face masks fed by a line supplying air for breathing. The applicators wear slip-on boots over shoes. The leg cuffs of the coveralls are taped to the boots. The applicators also wear rubber gloves or the same type of latex gloves used by doctors.

"The Tyvek suit has a hood, so the applicator is totally covered for protection from the substance he's spraying," Ash says. "We test the air in the tank before the applicator enters to ensure there is no hazard."

Symet workers drop lines that supply Grade D breathing air and the application substance through the tanker manway. Electric air compressors supply filtered air that is monitored for carbon monoxide.

Symet does the initial "L" inspection after completing application of a tanker lining. Besides a visual inspection, Symet performs a holiday test to check for voids or holes in the paint film. For coatings less than 30 mils thick, the holiday test is run at low voltage (6712 volts). Coatings more than 30 mils thick are spark-tested at 100 volts per mil of coating.

Commenting on the outlook for the tank trailer lining business, Ash says he believes the business will continue to grow, but at a slower pace.

"Some bulk carriers seem unaware of the benefits of tanker linings," he says. "Most tank trailers that are purchased are not lined, although a few large carriers are proactive on using lining systems. Lining tank trailers provides longer service life by preventing chemical corrosion of the tanks."