Corrosion Control

By Kerry Pianoforte, Editor | February 24, 2015

Corrosion control is especially important when dealing with high value substrates such as offshore oil rigs and other industrial structures meant to withstand harsh environments.

Protecting a substrate from corrosion is one of the most important functions of a coating. Corrosion control is especially important when dealing with high value substrates such as offshore oil rigs and other industrial structures meant to withstand harsh environments.

Axalta Coating Systems provides both liquid and powder coatings. Its liquid portfolio includes both waterborne and solventborne
products that vary by resin chemistry and inhibitive and barrier pigmentation packages to meet corrosion protection goals.  “Last year we relaunched globally all of our E-Coat products under the AquaEC name, which continues to include a range of products designed for both OEM and a range of industrial applications. Customers can choose electrodeposition or optimized sprayable formulations that are made out of alkyd, urethane, acrylic, or epoxy systems,” said Axalta’s research manager, Brian Priore.

Hempel is a world-leading supplier of protective coatings to the decorative, protective, marine, container and yacht markets. “In all these segments, we offer a broad product portfolio and a range of specialist coatings for specific sub-segments, corrosive conditions, substrates and applications,” said Andreu Tarve, Hempel Group Assortment manager.

“Wherever we work, we aim to provide products that add value to a customer’s business, whether it is through long-term maintenance savings, energy savings or some other benefit, and we have a number of products and technologies that achieve this. All these products and technologies are always coupled with expert technical service.”

PPG Protective & Marine Coatings is widely recognized as a world leader in protective and marine coatings, developing innovative products that are designed to deliver value and protection of its customers’ assets.  “PPG offers coatings solutions in all three key categories including Barrier Coatings, Sacrificial Coatings and Inhibitive Coatings,” said a spokesperson at PPG.
When choosing a corrosion control stytem, customers need to consider their specific requirements.

“There are many anticorrosive systems employed to afford the protection against corrosion –  it really does depend upon the lifetime requirements of  the asset owner,” said Neil Wilds, technical manager, Protective Coatings at AkzoNobel. “Many major oil companies now ask for coatings to be prequalified. This process involves the testing of coating systems to stringent international anticorrosion standards such as ISO 20340, for example. Only when they pass these tests will they be allowed on certain assets. Typical coating systems could be inorganic zinc-rich primers as part of a coating system, organic zinc-rich primers as part of a coating system, aluminium pure epoxies, zinc phosphate pigmented primers as part of a coating system, high-builds epoxies and glass flake pigmented coatings i.e. epoxies/polyesters.”

"There are also lots of other criteria, not just corrosion protection that form part of the process,” Wilds added. “In some cases, abrasion resistance or resistance to chemicals is also required.”

Choosing the correct corrosion protection technology for high value assets is not an easy task. There are several factors that must be taken into account to select the appropriate corrosion protection coating. 

“First, factors related to the substrate itself must be considered,” said Axalta’s Priore. “These include the type of metallic substrate and its inherent susceptibility to corrosion, shape complexity – curved surfaces, edges, corners, crevices, surface preparation – roughness and cleanliness – dirt, oil, grease, rust. Next, environmental and operating conditions must be taken into account.  In manufacturing, regulatory and emission requirements can vary between jurisdictions necessitating the selection of compliant systems.  In use, exposure to harsh conditions such as temperature, corrosive liquids and gases and mechanical wear and their duration will guide the coating choice.”

“Finally, customer specific attributes play a critical role,” he concluded.   “These can include cost, color, and ease of application.  The related durability requirements/warranties with respect to structural integrity and color/gloss retention are also a factor.”  
Another key conside
ration is the added value the corrosion sytem brings to the table. “Any good coating should add value to the customer’s business, whether this is a reduction in long-term maintenance, increased production speeds, lower VOCs, reduced energy use or improved hygiene,” said Tarve. “This value-add should be one of the main considerations, as it often leads to a higher long-term return on investment.”
In general, Tarve said, the main factors to consider are the external or internal environment in which the structure or equipment is operating in, as this environment is what causes corrosion; the substrate that needs to be protected; the surface preparation that is possible; the desired life expectancy and maintenance requirements of the system; the required application techniques, temperatures and equipment; and health & safety and legislation on the application site as well as the site where the structure or equipment will be used.
“Our sales teams guide customers through the selection process to ensure they choose the best coating for the project,” Tarve explained. “Also, as application is so important, we have more than 600 NACE/FROSIO certified coating advisors on hand to help and advise customers during application.”
Substrate Preparation is Key
Surface preparation and application are crucial to getting the best performance from a paint system and should be performed correctly. “A higher-end coating will not perform as expected if these two are not in place,” said Tarve. “However, a low performance system will deliver higher than average performance with a high standard of surface preparation and application.”

It is extremely important for the coatings to last the lifetimes that are being asked by customers. “There is little point spending a lot of money on a coating system if the surface preparation is substandard – it will just lead to early failure and then costly maintenance,” said Wilds. “The cost to re-apply a coating system offshore can be 10-15 times that of the cost in a painting shop onshore.”

For optimal performance, both the liquid coating system selection and the surface preparation must work hand in hand. “However, in some cases, a customer’s processes may not result in optimal substrate cleanliness and profile,” said Axalta’s product director for its liquid coatings business, Marko Strukelj. “In these instances, appropriate coating system selection can help to offset the non-ideal conditions as much as possible. The cost of the entire coating system and the expected durability can be negatively affected by substrate surface preparation.  There are, however, other options to be considered that may help improve performance, like applying thicker layers of coating and/or using high quality paint products such as Corlar undercoat and Imron topcoat.”

When selecting a coatings solution for corrosion protection, priority is placed on the substrate and its environment.  “PPG is highly skilled at crafting product solutions to provide protection in the harshest environments which may require chemical or moisture protection,” a spokersperson for PPG said. “Our highly trained and dedicated team of sales and technical representatives will evaluate these needs and create a customized coatings solution that will exceed the customer’s expectations. “
Customers expect productive and user-friendly coating systems.  “Many are sensitive to the environmental impact of their operations and prefer reduced volatiles and minimal waste from the products that they use,” said Strukelj. “They also expect efficient surface coverage, good coating thickness, and film density.  Finally, they look for superior long-term corrosion protection from various environmental factors such as chemical, ultraviolet radiation, abrasion and scratch & mar performance, and seek robust film properties such as excellent adhesion and chip resistance to various properly prepared substrates.  Overall, they want a brand name that they can depend on and a durable coating.”

According to Wilds, customers are now asking for guarantees up 20-30 years for offshore assets. “Unlike the marine market, the offshore asset does not come back to dock every five years for inspection,” he said. “A fixed-platform of FPSO (floating production, storage and offloading facility) can be offshore easily for more than 25 years. In the North Sea, for example, there is a lot of extension of the lifetime of platforms and therefore a lot of maintenance painting.”

“In high value infrastructure such as stadiums, airports and bridges, the focus is also on low-maintenance systems, as they are constantly in use by the public and are often very hard to access,” he added. “There is a large focus on aesthetics in this market so chemistries such polysiloxanes and fluoropolymers are being utilized.”

Tarve said that Hempel’s customers expect a long-life and reduced maintenance. “The main reason for having a coating system is to ensure the equipment or structure can remain in operation for long as possible, with maintenance only required during planned stops,” he added. “Many of our anti-corrosive coatings systems, for windmills and storage tanks for example, last for 20-30 years with only small repair work required during the asset’s lifecycle. The goal, however, is to create coatings that perform for 25+ years before requiring maintenance. AvantGuard technology is a big step towards reaching this goal.”

Hempel is focusing on all new technologies that can help increase the lifetime of the system and/or help customers achieve additional benefits. “Much of our work is focused on hybrid technologies, such as using the long UV durability of polisiloxanes to boost the effect of epoxies. We are also working with the newest polymer hybrid technologies,” said Tarve.

“A consideration for health, safety and the environment is also a natural part of our work and we develop products that meet or exceed both technical specifications and environmental legislation,” Tarve continued. “We are committed to phasing out lead, for example. Our decorative assortment is already lead free worldwide and we are implementing a new lead-free tinting system for industrial and marine products, which will be introduced in the second quarter of 2015. We will keep investing in R&D to improve our assortment, taking into account the environment without compromising the performance of our coatings. Our success is based on high performance, environmentally friendly and efficient coatings.”
Axalta continues to conduct and sponsor research to expand the understanding of mechanism and detection of corrosion. “We focus on accelerated methods that aim to result in excellent correlation to field performance,” said Priore. “Axalta is focusing on enhanced product service life through improved barrier coatings as well as next generation anti-corrosion pigment packages. We are excited about the direction the protective coatings industry is going with regards to the  use of new materials and additives that have novel chemical, electrical, mechanical, and thermal properties that impede reaction mechanisms and slow down corrosion rates.

New Products
A number of Axalta’s powder products are specifically designed for corrosion protection applications. Nap-Gard fusion-bonded epoxy (FBE) powder coatings are widely used to help protect pipeline structures from corrosion. They are formulated to offer enhanced physical and chemical stability, resistance to soil stress, adhesion to metal, and resistance to abrasion and corrosion mitigation.  

Alesta ZeroZinc powder coatings are also designed to protect against corrosion.  “ZeroZinc meets the standards for corrosion protection of steel structures by paint systems according to ISO 12944-6 and also fulfills ISO 12944-6 requirements for corrosivity category C5-I,” said Bill Sante, director of marketing and business development for Axalta’s powder business. “In combination with an adequate pretreatment, the primers are designed to provide durable, best-in-class corrosion protection under very aggressive atmosphere, high humidity, and extreme climate conditions.  Alesta ZeroZinc Steel Prime is designed to protect ferrous metals from corrosion. Thermoplastic powder coatings also meet corrosion protection objectives. Finally, our Abcite line of powder coatings is formulated for toughness and chip resistance without a primer undercoat and is designed to provide excellent corrosion and UV protection on exterior surfaces exposed to tough environmental conditions.”

Among Hempel’s latest offerings is AvantGuard technology (activated zinc), a new zinc technology that increases zinc activation to significantly improve the anti-corrosive performance and mechanical strength of the coating without increasing zinc content. AvantGuard-enabled products ensure lower long-term maintenance costs and high application productivity. Hempel currently produces three AvantGuard-enabled zinc primers: HEMPADUR AvantGuard 550, HEMPADUR AvantGuard 750 and HEMPADUR AvantGuard 770.

Hempel’s Galvosil (zinc silicate) coatings are heavy-duty zinc-rich anti-corrosives that provide excellent galvanic protection in moderate to severe corrosive environments. Some of these are reinforced with the company’s proprietary micro-fiber technology, which improves crack and impact resistance to reduce long-term maintenance costs.

Some of the key corrosion protection coatings offered by PPG Industries include the Novaguard Tank Lining Series, two-component, solvent-free, amine-cured novolac phenolic epoxy coating; apatented, value-added product – PSX 700, a two-component epoxy polysiloxane; AMERLOCK 2, a fast dry, self-priming epoxy and a newly released ONE Series of products providing industrial level performance in the convenience of a single can.