Corrosion Resistant Coatings

A number of factors go into designing a successful corrosion prevention program. Choosing the right corrosion resistant coating is only one of them. Another, which will determine the longevity of a corrosion prevention system, is maintenance. When the right industrial coating is chosen, and maintained, corrosion can successfully be stopped from damaging your asset. Corrosion services should be catered to your specific needs.

Selecting a Corrosion Resistant Coating

Sacrificial and barrier coatings have been engineered to excel in specialized circumstances and to respond to a number of very specific environmental pressures. A project’s specification sheet should address any special circumstances surrounding an asset, including any extreme pressures it should expect to encounter and whether or not a corrosion resistant coating will need to account for.

Here’s where it may not be a bad idea to enlist the services of a NACE-certified coatings inspector to view an asset before it’s coated. This will help to determine what properties will be required from a coating, such as whether a highly corrosive environment will necessitate a urethane topcoat rather than an alkyd, for instance. The number of possible environmental stresses, and the coatings that could stand up to them, are numerous. That’s why it’s often a good idea to have a professional inspection before selecting a coating.

Once a generic coating type has been selected, it’s important to consider where the product comes from. Many manufacturers will cut corners on the way to producing what many qualify as an “epoxy primer” or a “polyurethane finish”. Inferior resins and cheap fillers and extenders are shortcuts that can yield a less expensive product at the expense of performance.

Having your asset examined by a coatings specialist beforehand will also help with that all-important second step in keeping corrosion at bay: a well thought out maintenance plan.

Coatings maintenance

The worst possible time to discover your corrosion prevention system has let you down is when an asset fails. And protection from corrosion is, unfortunately, not a one-and-done process. The elements degrade. Chemicals erode. Moisture seeps in. These are realities as certain as death and taxes. But, with a coatings maintenance plan in place, regular wear over time needn’t be a significant setback.

A little spot coating as a part of a regular coatings maintenance plan can prevent the spread of localized corrosion and keep the need for a full-blown recoat years in the future.

And that’s not the most significant reason for having a maintenance plan in place. A full-scale failure as a result of damage caused by corrosion could be catastrophic. Leaking chemical pipelines and unsound structural steel threaten lives as well as financial stability. We’ve seen already how much corrosion costs the economy, and regular coating’s maintenance is a one of the best fundamental strategies we have for bringing those expenditures down. When corrosion is allowed to proceed to the point of taking an asset out of commission, that’s corrosion at its most expensive, not to mention its most dangerous.

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Corrosion Services: Preventing Corrosion

We’ve discovered more than a few effective methods for protecting steel from corrosion. Some methods have been in use for longer than others, some are better for the environment than others, and all of them entail certain tradeoffs as far as performance, price and material properties are concerned.

The corrosion services you receive need to reflect the conditions your assets endure. Environmental factors such as acid rain, humidity, chemical salts, oxygen and high temperatures are all factors that can affect the pace of corrosion. It’s best to control for these factors where possible, but this is often impractical or downright impossible. For more reliable methods of corrosion prevention, more active solutions are called for.

While many methods of corrosion prevention have been tested out over the years, a couple of them have emerged as among the most effective. Corrosion resistant coatings are among the most reliable and cost-effective methods for fighting corrosion. For reasons of chemistry, coating structural steel in gold would probably be fairly effective in protecting it from corrosion. But for more obvious reasons, this is not a widely used method of corrosion control.

Within the realm of protective coatings, a few strategies have emerged as particularly effective corrosion services. It’s no coincidence that two of them, barrier and sacrificial coatings, are among the coating services that we specialize in.

Here’s a top-level breakdown of the strategies most of our products use to battle corrosion:

Sacrificial coatings

Sacrificial coatings tend to make excellent primers. These unselfish coatings usually take the form of an extremely thin layer of metal, such as zinc or nickel, which is known to corrode preferentially to steel. These coatings are applied directly to a ferrous metal, usually steel, in order to steer the corrosion process in a direction that is ultimately not harmful to the asset by “donating” an electron to the substrate to make its charge unfriendly to the corrosion process.

Zinc primers are excellent examples of sacrificial coatings. Though they’re meant to corrode preferentially to the asset, the rate at which they succumb to corrosion is slower than many other sacrificial coatings, leading to longer intervals before a recoat is necessary.

When combined with a topcoat system that offers excellent barrier properties, sacrificial primers form part of a system with proven success in fighting corrosion.

Barrier coatings

Barrier coatings are probably the products that come to mind when most people think of industrial coatings. These are the products in charge of keeping oxygen and moisture from a substrate and protecting it from harmful chemicals, including soluble salts.

According to NACE, the following are the most important properties for a barrier coating. A coating should:

• Be able to protect from the surrounding chemical environment
• Be able to resist moisture
• Be able to resist vibration and minor impacts
• Exhibit strong adhesion properties even in moist conditions
• Exhibit strong wetting properties for a smooth, even film build

Different environments stress barrier coatings in different ways. In areas experiencing prolonged exposure to sunlight, a high UV-resistant coating will be a priority. In marine environments, a coating’s ability to protect against soluble salts and their corrosive effects will be especially important. In chemical factories and other processing facilities, where harsh and reactive materials are an everyday reality, good chemical resistance will be a necessary property.

Given the wide array of elements barrier coatings must protect against, it’s a good thing they’re not working alone. When combined with a sacrificial primer, and sometimes an intermediate barrier coating, a good barrier coating is part of a system that effectively fights corrosion.

But it’s important to know exactly which system is called for given an asset’s environmental circumstances. That’s why we offer on-site surveys as part of our corrosion services.

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Common Types of Corrosion

The nation’s crumbling transportation infrastructure, and the lack of funding it receives, is making headlines on a daily basis these days. While there are many causes for collapsed bridges, potholed highways and inefficient railway networks, one natural phenomenon stands out as a threat to nearly every sector that falls under the umbrella of “America’s transportation infrastructure problem.” The National Association of Corrosion Engineers (NACE) estimates that corrosion costs the U.S. economy $276 billion annually.

More than just something unpleasant to look at, corrosion represents a serious drag on the economy and a danger to human health and safety. It is a natural, albeit preventable, process that’s spawned an entire industry dedicated to battling it. Corrosion services have become an important part of maintaining steel and iron assets.

Broadly, corrosion is defined as the naturally occurring degradation of a surface (usually a metal), when exposed to the atmosphere. A more relevant definition for our purposes concerns what happens to iron, a major component of steel and the most commonly used alloy in infrastructure, when it is exposed to the elements.

When iron is exposed to oxygen and moisture, an electrochemical process known as oxidation occurs. Oxidation results in iron oxide, or rust, forming on the metal’s surface and corrosion begins to set in. As long as steel remains an integral component in the makeup of the country’s transportation infrastructure, corrosion is not a problem that will disappear anytime soon. 

Generalized Corrosion and Localized Corrosion

The many types of corrosion that can affect an asset add to the difficulty of protecting against it. Generally speaking, there are two, broad categories of corrosion: generalized and localized. As their names suggest, generalized corrosion attacks the entire surface area of an asset, while localized corrosion is limited to certain, often irregularly shaped, areas of a particular asset.

Because generalized corrosion is predictable, treatable and fairly easy to detect, it’s often seen as the less dangerous of the two types, assuming prevention methods are in place initially. Localized corrosion, on the other hand, can be more difficult to detect and is more likely to occur even after an asset has apparently been protected. Here are the most common localized corrosion types, according to NACE:

• Pitting corrosion– Pitting corrosion is the result of localized failures in a coating system. At these points of failure, small holes begin to form and increase in size if the problem is not addressed. Because pitting corrosion is more difficult to spot, and often occurs on assets that owners consider adequately protected, pitting corrosion is much more likely to progress to the point of seriously degrading the integrity of an asset, making it a far more dangerous type of corrosion.
• Crevice corrosion– Also sometimes called “contact” corrosion, crevice corrosion occurs in those micro-spaces where two different materials overlap or otherwise touch one another. This could be a metal-on-metal or metal on a non-metal point of contact, but it usually occurs around bolts, gaskets, washers, clamps or other fastening devices that form small spaces where corrosion process can begin.
• Filiform corrosion– Filiform corrosion occurs when moisture is allowed to penetrate the small gap between a coating and the substrate, usually at a natural edge on the substrate or at a defect in the coating system. This type of localized corrosion is often distinguishable by bubbles forming beneath the coating.

The most successful method for controlling these types of corrosion involves the one-two-punch of an effective prevention strategy and diligent upkeep of that means of prevention.

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VOC regulations and what they mean for manufacturers

Volatile organic compounds, or VOCs, are emitted by everything from aerosol deodorants to household cleaning supplies. But some industries may create them in large enough quantities to constitute a substantial health risk and contribute to ground-level ozone buildup.

According to the EPA, ground-level ozone results from a reaction between oxides of nitrogen and sunlight. It is associated with a host of respiratory issues.

Residents of some large cities, such as Los Angeles or Beijing, are familiar with the buildup of smog over the city skyline. VOCs are a major component of smog. But whereas Los Angeles began to regulate emissions in the 1970s and resulting in a reduction of ground-level ozone levels, Beijing did not enact major air pollution control measures until 2013 and still experiences exceptionally smoggy days.

Inventions like the catalytic converter have been instrumental in cutting pollution, but so too have regulations on the output of VOCs in industrial settings. While VOC regulations may sometimes be a thorn in the side of high-output facilities, they’re nothing compared to the health effects that can result from heavy exposure to ground-level ozone from VOCs.

VOC regulations by state

Coatings manufacturers are limited in the number of VOCs they can include in coatings by the EPA’s Architectural Coating Rule for Volatile Organic Compounds. Enacted in 1998, this subset of the earlier Clean Air Act sets nationwide rules for the manufacture, labeling and packaging of coatings to be used on any stationary structure.

In 2020, the EPA enacted the National Emission Standards for Hazardous Air Pollutants, which establishes emission limits and work practice requirements for new and existing miscellaneous coating manufacturing operations like process vessels, storage tanks, wastewater, transfer operations, equipment leaks, and heat exchange systems. It also implemented the Clean Air Act to require new emission-control techniques under Maximum Achievable Control Technology standards.

Nearly every industry also has its own regulations controlling for VOC emissions. State regulations must meet what the EPA calls Reasonably Available Control Technology (RACT), or the lowest VOC emission levels that can be achieved given technological and economic considerations. Some states and counties go even further. States like Pennsylvania and California have enacted VOC regulations that are far tougher than the EPA’s.

How low-VOC products can help business

VOC regulations don’t have to be the limiting factor in production for manufacturers. OEM and other operations using large amounts of industrial coatings have low-VOC options. These can help keep manufacturers running at full bore.

We’ve written on this blog before about 100% solids coatings. These are coatings that contain no solvents, and hence no VOCs. While these coatings tend to come with a higher sticker price than a similar coating containing VOCs, they also cover a much greater surface area. In many cases, this can make the price difference a relative wash.

Water-based coatings are another option for manufacturing operations to reduce VOC output. While these coatings may have had longer curing times in the past, newer hybrid formulations and other methods of forced curing have largely solved this issue. These products can also help to remove the need to artificially slow production in order to stay beneath VOC emission limits.

If you’re interested in discussing low or zero VOC coatings further, we’d love to talk. You can get in touch with us here.

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