O&M, Plant Optimization

Can chemically bonded phosphate ceramic coatings stop corrosion in the utility industry?

From gas distribution, drinking water, and sewer piping to electric transmission, distribution, and substation structures, to telecom towers, much of the utility industry’s carbon steel facility infrastructure is aging and now between 40 and 100 years old.  Consequently, the cost of corrosion is on a path to dramatically escalate.

“Utilities, which supply gas, water, electricity and telecommunications services, account for the largest portion of annual industrial corrosion costs, with direct corrosion costs totaling $47.9 billion, according to NACE International’s report Corrosion Costs and Preventive Strategies in the United States.

The Electric Power Research Institute (EPRI), a non-profit scientific research organization, estimates that corrosion cost the electric power industry $17 billion in 1998, of which “about 22 percent of the corrosion costs were considered avoidable.”

Once corrosion starts, often through a breach in traditional barrier-type coatings such as epoxies or polyurethanes, the coating can act like a greenhouse, trapping water, oxygen and other corrosion promoters.  This allows the corrosion to spread quickly under the coating itself, which is difficult to inspect, and can lead to failure and costly premature replacement.  For these reasons, such coatings are routinely reapplied at a sizeable cost in facility downtime, surface preparation, and coating application.

“Corrosion is a never ending problem to utility facility infrastructure, and everything made of steel is at risk,” said Scott Taylor, President of Taylor’s Industrial Coatings, a Lake Wales, Florida based industrial coatings contractor.  “Steel structures are typically recoated every seven to 10 years, depending on environmental factors such as rainfall, humidity, and proximity to a marine environment.”

Now a new generation of anti-corrosion coatings, called chemically bonded phosphate ceramics (CBPCs), is poised to cost-effectively stop such corrosion, improve safety, and significantly extend utility industry infrastructure and facility life while minimizing maintenance and downtime.

Protecting Utility Assets for Decades

“Utilities are looking for better corrosion coatings that extend the usable lifespan of their facilities while minimizing the need for coating reapplication,” said Taylor, whose company has coated a wide range of utility infrastructure including gas and circulating water piping, waterbox/tubesheets, boiler structures, turbine decks and enclosures, ct inlet filter houses, interior/exterior tanks, as well as transmission/distribution poles and towers.

To address this particular situation, the company turned to EonCoat, a spray applied inorganic coating from the Raleigh, North Carolina based company of the same name.   

In contrast to traditional polymer coatings that sit on top of the substrate, the corrosion resistant CBPC 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 like oxygen and humidity to get behind the coating the way they can with ordinary paints.

Although traditional polymer coatings mechanically bond to substrates that have been extensively prepared, if gouged moisture and oxygen will migrate under the coating’s film from all sides of the gouge.

By contrast, the same damage to the ceramic-coated substrate will not spread corrosion in utility facility infrastructure because the carbon steel’s surface is turned into an alloy of stable oxides.  Once the steel’s surface is stable (the way noble metals like gold and silver are stable) it will no longer react with the environment and cannot corrode.

Visible in scanning electron microscope photography, the coating does not leave a gap between the steel and the coating because the bond is chemical rather than mechanical.  Since there is no gap, even if moisture was to get through to the steel due to a gouge, there is nowhere for the moisture to travel, which effectively stops corrosion in utility industry applications.

Taylor’s Industrial Coatings has recently successfully spray applied the coating to 3,000 linear feet of 24” gas pipe at an electric power generation facility in the southeast U.S.

“The new anti-corrosion approach triples the expected lifespan of traditional coatings and is much more cost-effective in the long run for utility facility and infrastructure managers who want to protect their assets,” said Taylor

For corrosion protection projects using typical polymer paints such as epoxies or polyurethanes, the cure time may be days or weeks before the next coat of traditional ‘three part systems’ can be applied, depending on the product.  The cure time is necessary to allow each coat to achieve its full properties, even though it may feel dry to the touch.

With traditional coatings, extensive surface preparation is required and done a little at a time to avoid surface oxidation, commonly known as ‘flash rust’, which can require re-blasting.

“Typically you need to keep an SP 10 throughout the entire blast operation, cleaning operation, and painting operation with traditional coatings,” said Wesley Newburn, a quality control manager for Mobley Industrial Services, a multi-service specialty contractor.  “You may need to rent D-H equipment because humidity above 60 percent will oxidize the surface and require re-blasting.”

In contrast, a corrosion resistant coating for carbon steel utilizing the ceramic coating in a single coat requires almost no curing time.  Return to service can be achieved in as little as one hour.

About the author: Del Williams is a technical writer based in Torrance, California.