Opinion: Coating Crucial to Stopping Tank Corrosion

This Opinion piece appears in the Dec. 5 print edition of Transport Topics. Click here to subscribe today.

By Merrick Alpert

President

EonCoat

In truck and rail tankers and beyond, chemically bonded phosphate ceramics can stop corrosion, improve safety, extend equipment life and minimize maintenance and downtime.

Thousands of chemicals, petroleum products and corrosive elements such as salt-water brine are transported by tanker truck, railcar and distributors. They also can be found in chemical tanks at facilities and refineries.

In these venues, carbon steel corrosion can require early tank replacement and maintenance, as well as pose a safety risk in terms of potential leaks, spills and even fire and explosion, making effective corrosion protection a must.

Alpert

That protection could be found in chemically bonded phosphate ceramics, which are said to help mitigate corrosion in trucks, rail tankers and other places. It also can improve safety, extend equipment life and minimize maintenance and downtime.

Joe Svehlak, facility manager at DFW Tank Cleaning, a Dallas- Fort Worth, Texas-based full service tank cleaning facility that specializes in chemical cleaning, said that protecting against corrosion is vital in such tanks, as it is in the facility flush tanks.

According to Svehlak, effective corrosion resistance is essential in flush tanks because they hold the wastewater, which can include residual chemicals, from the first flushes of tanks that the company cleans, until it is treated. This amounts to thousands of different residual chemicals held in the flush tanks annually — from petroleum products and salt-water brine to fluoride, caustic soda and a variety of acids.

Against such tank-corrosion challenges, traditional polymer paints and rubber-type coatings have long been used as physical barriers to keep corrosion promoters such as water and oxygen away from steel substrates. This works until the paint is scratched, chipped or breached, and corrosion promoters enter the gap between the substrate and coating.

Truck or rail tankers hauling waste, including sand and sediment, also can be particularly prone to scratches, chips or breaches. Then the coating can act like a greenhouse — trapping water, oxygen and other corrosion promoters — which allows the corrosion to spread.

Now a new generation of anti-corrosion coating, called chemically bonded phosphate ceramics, or CBPC, is poised to stop such corrosion, improve safety and extend tank life in the transportation industry and beyond while minimizing maintenance and downtime.

To control corrosion, a tank-cleaning facility chose a company specializing in steel construction and industrial plant building projects to coat the inside of two flush tanks. The flush tanks were coated with a spray-applied inorganic coating — a new category — CBPCs that can stop corrosion.

In contrast to traditional polymer coatings that sit on top of the substrate, the corrosion-resistant coating bonds through a chemical reaction with the substrate, and slight surface oxidation actually improves the reaction. An alloy layer is formed.

This makes it impossible for corrosion promoters such as oxygen and humidity to get behind the coating as they can with ordinary paints. The corrosion barrier is covered by a ceramic shell that resists corrosion, fire, water, abrasion, chemicals and temperatures up to 200 degrees Fahrenheit.

Visible in scanning electron microscope photography, these new coatings do not leave a gap between the steel and the coating because the bond is chemical rather than mechanical. Because there is no gap, even if moisture were to get through to the steel in a gouge, the moisture has nowhere to travel. The only spot that can corrode is the scribe line itself, which eliminates the possibility of the corrosion migrating.

Unlike traditional methods, the corrosion-resistant coatings for mild steel have a double layer of protection. The tough, outside ceramic coating will not chip like paint and takes sandblasting to remove. The chemically bonded layer stops corrosion and will not allow corrosion promoters to spread.

It also resists tank corrosion when transporting other products such as petroleum or even used restaurant waste — oil, fat or grease.

For transportation companies looking to reduce costs, CBPC coatings offer additional advantages beyond corrosion resistance. They include quick return to service that minimizes equipment downtime, as well as no volatile organic compounds, no hazardous air pollutants and a flame spread rating of zero, which improves safety.

The new corrosion-resistant coating for carbon steel applies in a single coat and requires almost no curing time. Return to service can be achieved in as little as one hour. This speed in getting a tank, tanker truck or railcar operating again can save significantly in reduced downtime.

The new category of coating consists of two nonhazardous components that do not interact until applied by a plural spray system like those commonly used to apply polyurethane foam or polyurea coatings. Because the coating is inorganic, there are no VOCs, no HAPs and no odor. This means that the coating can be applied safely, even in confined spaces.

Alpert has decades of experience in the energy industry. EonCoat, based in Raleigh, North Carolina, is a coating company.