Coatings in harsh environments already have a tough job protecting metal and plastic components in cars, ships, planes, and industrial machinery. But a combination of globalized markets, more extreme operating requirements, and the desire for a cleaner environment are demanding more from the coatings.
Some manufacturers are combining the product’s basic function, whether it’s resistance to salt water, chemicals, or extreme temperatures, with additional features such as increased durability, reduced friction, lower cost, or less wasteful application. Some classes of coatings are replacing a competing class in certain applications. In other application areas, new coating types are gaining ground.
Field-applied coatings are used as topcoats on metal structures with tanks or piping exposed to outdoor conditions, such as bridges, oil tankers, or chemical plants. Traditionally, a zinc-rich primer coat was used to protect metal from corrosion, Jerry Witucki, senior coatings specialist for Dow Corning’s coatings and composites group, told us. The zinc powder protects the steel via sacrificial oxidation. An epoxy coating is applied to hold down the zinc and provide corrosion protection, followed by a polyurethane topcoat.
Henkel’s electrodeposited Alodine EC2 titanium oxide coating can be used on a variety of aluminum castings, extrusions, and wrought alloy parts for superior corrosion resistance in harsh environments.
“It’s possible to cut down the number of coatings and get the same level of protection for less labor cost and downtime,” Witucki said. “Siloxane-based coatings have superior weather and chemical resistance. The same zinc-rich primer is covered by a silicone acrylic or silicone epoxy topcoat. These are being used on offshore oil platforms, wind farms, radio towers, transmission lines, and anywhere steel is outside.”
Because of industry consolidation, field-applied coating systems have become commoditized, he said. Now coatings suppliers are differentiating their products by incorporating a new benefit or performance enhancement, such as durability, easy cleaning, or chemical resistance. “Historically, the silicones were relegated to niche applications due to cost, but as the price of organic resins increases with the price of oil, siloxanes have become a more attractive option.”
One of the fastest-growing coating technologies in industrial maintenance is the silicone hybrid coating, which combines the best of organics and silicones. In particular, polysiloxane hybrids combine silicone with epoxy, acrylic, or urethane. “Polysiloxanes have inherently low viscosity, so there’s low solvent requirements. They have good thermal and UV stability, excellent chemical resistance, and excellent compatibility with organics.” Their share of the coatings market is still small, but engineers increasingly prefer hybrids, so rapid growth in polysiloxane use is expected.
Thanks, Jack. I'm not familiar with food processing--and each time I learn something about it, I must say the "Ecchh" factor tends to apply. In fact, I basically don't eat processed foods because of all the additives and excessive amounts of salt. Anyway, your description certainly fills out the picture of how harsh an environment processed food ingredients create in a plant.
Ann, don't forget about all the concentrates from juices to sauces to soda that might be fine when you consume them but are in a totally different state in the plant. There are also the unpronouncable ingredients that are in a small measure in the final product but great quantities there. Also, the main ingredient in just about everything seems to be salt. If it can take out an unprotected car over a winter, just imagine what it can do in quantities inside a moist food plant.
Thanks for the reply, TJ. I don't tend to think of foods as a harsh substance, more of a messy one, but you've certainly got a point. At least I can easily think of ketchup, mustard, and pickles, for example, which are all highly acidic.
I have nothing specific in mind, Ann. I've dealt with food processing environments quite a bit, and am amazed at what the food alone can do, let alone the caustics used to clean machinery.
TJ, the coatings I reported on are designed for use in harsh environments, such as aerospace and transportation, as well as bridges and other large structures exposed to weather, and some industrial environments. To my knowledge, none of these objects or their coatings are involved in, or designed for, direct food contact, and so AFAIK are not regulated by the FDA. However, I did not ask that question since it was not the focus of the article. Did you have something specific in mind?
TJ, I don't have any present plans to cover EPA approval or regulations of coatings in a major feature, but might report on this in a blog or news story if something newsworthy happens. What do you have in mind?
Thanks, TJ. You're right, stainless is well-known for being corrosion resistant. One thing I would have liked to explore was exactly what you point out--the fact that penetration and wear do occur. This was addressed to some extent by my sources, but monitoring processes and techniques are really a separate subject.
Your impression is VERY accurate. Stainless steel ISN'T. It's corrosion-resistant. Coatings can do better, but when put to use they must be monitored for wear. As soon as a penetration occurs, be it through wear or external damage, the part must be replaced or recoated.
Ann, will you be covering FDA approval of coatings in any of your reports?
Thanks for the feedback, guys. Chuck, I specifically looked at coatings that are targeted for harsh environments. And I didn't look for raw number volumes, just specific apps where these are used. Within those parameters, I got the impression that anti-corrosion is a big deal, maybe the biggest deal, for various reasons.
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