Chemical attack

Chemical reactions are the lifeblood of process plants, but their interaction on the exposed surfaces of valuable plant equipment can often cause unwelcome side effects.

Many vessels and instruments used in process plants are under constant attack from chemical solutions accelerated by elevated temperatures and abrasive materials, says Belzona commercial director Steve Cooper.

“Historically we have repaired equipment that has reached an age where it has already corroded

Belzona commercial director Steve Cooper

Corrosion can result in dire cost and safety complications, causing lost production time, unplanned shutdowns, and unsafe working conditions.

Restoring affected equipment is at the core of what Belzona does for its industrial customers, which are mainly from oil, gas, power and wastewater industries.

“Repair and reclamation go hand in hand,” says Cooper.

“So first we repair the corroded surface and then add protection against future corrosion.”

Repairing existing equipment such as tanks, vessels, pumps, valves, and pipelines are the most commonly requested services, however Cooper says he has observed a recent shift in the market as companies discover that lifecycle costs of running equipment are where most of their budgets are being eaten up.

“Historically we have repaired equipment that has reached an age where it has already corroded,” he says.

“But in the last five or six years we have encountered more clients wanting us to protect new equipment.”

This means coating them from new rather than putting them into service and then having to pull them out again in five years time.

“Quite often our coatings outlast the original equipment, particularly in the oil industry,” says Cooper. 

“Companies will also look at carbon steel vessels that are ‘Belzona lined’ so we often find ourselves talking to clients specifically about new-build work where we wouldn’t have [done so] six years ago,” he adds.

When it comes to developing new coating technology, Cooper says Belzona works hard to stay a step ahead of the pack.

“We’ve got a strong history in developing new materials and have recently introduced two new coatings into our product range,” he says.

The most notable of these is an upgrade to its flagship product for erosion and corrosion protection, which originally contained a lot of metal fillers in the cured product.

“This [product] is great for resisting erosion – particularly in aggressive environments where you have fluid flow that has proved particularly hard wearing,” says Cooper.

The problem with this coating, however, was that it couldn’t be applied using the normal spray method because the metal fillers would quickly wear out the application equipment.

“Our new coating gives the same level of corrosion and erosion resistance as before but has no metallic fillers, so in large areas it can now be applied with a spray application,” he says.

“The other benefit is you can test its thickness with conventional dry film testing.”

Some of the most challenging process environments he has encountered are within industries with moving water, slurries, oils or chemicals.

“Any type of equipment that is handling moving slurries or fluids presents big challenges, and some of those can be chemical as well, so anti-corrosion materials must also be resistant to chemical attack,” he says.

Corrosion and rust prevention is essential for metals used in environments where water, high humidity, mist and salt are factors, says Andrew Courtney, group operations director of Surface Technology.

Surface Technology provides a range of corrosion coatings for its customer base, which includes oil & gas and food & drink companies.

These are barrier coatings, which are non-porous and protect metal surfaces from corrosion, sacrificial coatings to provide a layer that corrodes in preference to the substrate, and Fluoropolymer coatings, which provide a thicker form of barrier protection for very aggressive environments.

“In-depth knowledge of substrate material performance, the type of application it will be used for, operating environment and expected performance levels are essential when selecting an anti-corrosion coating,” says Courtney.

“The drive to exploit oil reserves at greater depths, in more hostile environments and hostile operating conditions requires high performance coatings that can offer multiple functionality.”

This means components may require corrosion protection allied with other elements such as low coefficient of friction, prevention of marine growth, high-pressure resistance and extreme thermal properties.

New developments in materials and methods of application are a driving force in the coatings market, Courtney adds.

However, the high risk associated with changing coating types on safety critical parts can restrict equipment designers from moving beyond current specifications and methods, he says.

This is exacerbated by the time taken to validate and test new coating materials, which means that the introduction of new coating technologies can take several years, he says.

The Restriction of Hazardous Substances and resulting bans of some chemicals have also impacted on the availability of certain materials used in coatings, says Courtney.

“This can sometimes require us to redevelop our existing coating to use alternative component materials,” he says.

Some companies are looking beyond coating technologies in the battle against corrosion.

Ham-Let Group, a global manufacturer of instrumentation valves and fittings for industrial and high-purity applications, has developed its own enhanced 316L stainless steel recipe for resisting corrosion.

The company designs and builds instrumentation valves and fittings for high pressure, high temperature and vacuum applications in energy, oil & gas, chemical and petrochemical industries.

The company’s new steel recipe is called PuRight, which is an enhanced version of 316L Stainless Steel, says Felix Shestatski, vice president of quality, engineering, and research and development.

The use of 316L stainless steel has been widely adopted for instrumentation components subject to corrosion, however Shestatski believes the current definition of the steel is applied too widely.

“Some steels with this classification demonstrate very poor performance [against corrosion], while others perform much better,” he says.

PuRight “is far more resistant to corrosion, he says, and is also suited to applications interacting with highly corrosive liquids and gases such as industrial gas manufacturers.

“This offers a clear advantage for its use in pressure or flow control devices, such as valves and fittings.”

Shestatski says Ham-Let is very cautious when it comes to introducing new products because of the plethora of industry specifications customers must adhere to, which restricts their ability to incorporate change.

“What we are trying to do … is understand the attributes of each material before we go about changing ingredients, so we can flag this up to our customers well in advance,” he says.