Selecting floor coatings to deal with water, corrosion, cracks and resurfacing

An overview of key factors and technologies for selecting floor coatings.

Floor coatings protect underlying substrates and provide easy-to-clean surfaces. Specifiers must consider many factors when selecting floor coatings for industrial plants. First is the substrate constructionconcrete, reinforced concrete or steel. Most plant floors are concrete. If the floor is on grade or designed for vehicular traffic, it's probably reinforced. Diamond plate steel often is used for loading docks and stairways.

The next critical factor is the floor's chemical and environmental exposure. The right coating withstands chemical splash, spillage, fallout and fumes. Chemicals that destroy concrete include sulfates (calcium, sodium, magnesium and ammonium), sugar, fermenting liquors, chlorides, fats and oils.

Other factors include foot traffic, rubber-wheeled or steel-wheeled vehicular traffic, microbial attack, high humidity, condensation, immersion and cleaning solutions.

Plant downtime also is important. Some coating systems are designed for fast application and rapid return to service. Regulations can be an issue in plants, subject to U.S. Department of Agriculture inspections. In others, some floor areas must meet slip resistance requirements of the Americans with Disabilities Act. Finally, aesthetically pleasing floors contribute to overall plant appearance and cleanliness.

In general, thin-film coatings usually are sufficient for floors subject to short-term or intermittent chemical exposure and light to moderate traffic. If chemical spills are fairly common, or severe abrasion is a factor, high build coatings of 10 to 30 mils, or even thick film toppings of 250 mils or greater are available.

Waterproofing

Most plants don't require waterproof floors. Exceptions include second-floor processing areas, pharmaceutical plants, parking decks or rooftop parking areas. Many coating types are available for these applications. A new flooring technology is polyurea. These coatings don't have the sweat-in time that's so common with conventional epoxy or urethane coatings. Polyurea provides a tough, flexible and abuse-resistant finish.

Polyurea coatings are based on proprietary urethane polymers and an amine-type curing mechanism that emits no volatile organic compounds or obnoxious odors. The coating can be applied in a single, stand-alone application at thicknesses from 10 mils to 250 mils or greater, either with a smooth or a non-slip functional finish, or as a base layer in a multi-coat system. Though application requires specialized equipment and trained, experienced applicators, polyurea coatings are an option when a tough, flexible, impact resistant, waterproof surface is required quickly.

Recent applications for these coatings include second-story processing areas above research laboratories in pharmaceutical buildings and parking garage ramps that experience heavy applications of salt to keep them free of snow and ice. A polyurea coating with aggressive skid-resistant trap rock aggregate protects the concrete and steel from the salt.

Corrosion control

Corrosion control is an issue not only for steel floors, but also for reinforced concrete. The most common industrial floor coating to control corrosion in these applications is a high-solids, two-component epoxy.

These are available in high build, self-leveling, high gloss and non-slip or anti-skid formulations. They can be applied to a prepared surface using a variety of methods, and they provide a durable finish that withstands cleaning solutions. Although a smooth, high-gloss finish is easier to clean, safety requirements, especially in areas with high foot traffic, may demand a textured finish, which is more time-consuming and labor-intensive to clean.

High solids epoxies may exhibit superior resistance to chemicals, moisture, abrasion and impact. The self-leveling types provide a seamless, durable, hygienic surface that can be applied to smooth or mildly spalled concrete, making them suitable for cleanrooms, laboratories, workshops and light assembly areas.

Crack treatment

Maintaining a floor coating requires repairing surface cracks or chips promptly to prevent dirt and dust from collecting there. Also, unrepaired cracks or chips may widen, contributing to premature floor coating failure and allowing the underlying substrate to deteriorate.

Evaluate and repair cracks, voids and other defects in concrete floors in accordance with American Concrete Institute guidelines (ACI) 224.IR-89. Generally, this means grinding out rough edges and using a crack filler, which is a two-component epoxy paste developed specifically for sealing, smoothing and fairing cracks in concrete, metal, plastics (FRP), wood or masonry floors. Fillers may offer resistance to salt water, oil, fuels and other chemicals.

Unlike cracks, seams or expansion joints are planned breaks that allow for floor movement. Seams also occur when a floor is too large to be painted in one pass. It's not unusual to paint a floor in units of 500 sq. ft. at a time, with seams resulting where pours abut. Feathering rough seam edges and using a joint sealant ensures a smooth finish.

Joint sealants are often hybrids, containing urethane and epoxy resins to provide a resilient filler for expansion joints as well as flexural strength and elongation properties while maintaining tensile strength. When evaluating joint sealants, consider adhesive strength and flexibility over the temperature range appropriate for the exposure.

Industrial resurfacing

Because minimizing plant downtime is a high priority when floors are resurfaced, many coatings cure quickly. One technology to consider is a water-based, urethane modified cementitious slurry mortar system. It's a good choice for resurfacing or sloping because the product can be installed without a topcoat, further speeding the return to service. These coatings resist impact and abrasion. They don't blister from moisture within the substrate, and can be counted on to provide durability, even in harsh environments.

The coating technologies to consider for food and beverage or pharmaceutical facilities, where seamless floors and a smooth floor-to-wall envelope are required, include water-based catalyzed epoxy coatings, flexible epoxy crack isolation systems and epoxy-terrazzo flooring, which tenaciously withstands abuse.

 

Unlike cracks, seams and expansion joints are planned breaks in the surface that allow for floor movement. Rough seam edges must be feathered and joint sealants used to ensure a smooth finish.

Application and inspection

Important factors to monitor during coating application and curing include thickness (wet and dry), ambient conditions and the temperature of the surface and material. Accommodate inspection by using a number of mandatory hold points, such as after surface preparation and after each coat has been applied. Document the data properly and retain it for future reference.

To achieve desired service life, protective coating systems require a regularly scheduled program of inspection, touch-up and maintenance. Inspect systems in severe exposure at least twice a year. Examine light-to-moderate exposure systems at 12-month to 18-month intervals.

Dave Schutz is a product information specialist with The Sherwin-Williams Co. He can be reached at dlschutz@sherwin.com or (216) 515-5277.

Figures: The Sherwin-Williams Co.

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