Effective chemical-resistant floor finishes

May 24, 2018

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All images courtesy Flowcrete Group

By Ben Smith
Getting the floor right in facilities employing corrosive chemicals is critical to ensuring the site can maintain a safe, hygienic, and efficient operational environment. However, choosing the optimum flooring solution is a difficult task because demands placed on the floor surface are usually underestimated. Sometimes, the chosen material cannot prevent the destruction of the concrete substrate as a result of chemical abuse.

The author has also witnessed many industrial floorcoverings failing within the first few years of service, creating enormous disruption and expense to the client.

Poor substrate prep, thermal shock, pH levels, and moisture content in the concrete can cause floor failure. This failure itself can manifest in many forms, with the most common being bubbling, cracking, and delamination. Depending on the scale of failure, this can be confined to a small, easily repairable area or it could affect the entire floor and require the coating to be entirely taken up and reapplied. Understanding the reasons or triggers leading to floor failure can help building professionals prevent such instances from re-occurring.

Resin flooring has become a popular choice for sites employing corrosive chemicals due to the system’s hardwearing and easy-to-clean properties. In the most abusive locations, such as secondary containment areas, the flooring would be a type of resin. For places that are a bit less intense (e.g. breweries), resin flooring is often competing with ceramic tiles, and in facilities like hospitals it could be competing against vinyl, linoleum, or rubber.

The surest way to avoid resin floor failure is to take the necessary preventive steps at the material specification stage itself by selecting fit-for-purpose, durable floor systems, designed to meet the operational demands of the individual environment alongside any health, safety, hygiene, and compliance regulations specific to the industry.

Additional benefits such as bactericidal agents, anti-slip aggregates, and static electricity dissipation can also be incorporated into the finish to meet site-specific needs. These properties can make a working space safer and more effective. For example, antibacterial additives can be incorporated throughout the matrix of a cementitious urethane floor so any contaminants in contact with the surface are being actively eliminated even when the floor is not being washed. Broadcasting aggregates into a resin surface creates a textured finish enhancing traction underfoot. One can also alter the coating’s slip-resistance properties by changing the size and quantity of the aggregate. Dissipating electrostatic charge is usually required in locations with sensitive electronic equipment or inflammable solvents or gases because static charge buildup can pose a dangerous ignition risk.

Flooring types
A range of resin flooring solutions, from thin floor sealers to heavy-duty industrial protection in various thicknesses, is available in the market. They can be tailored to suit specific onsite challenges. Many different types of chemicals are now employed to manufacture resin floors, but the one common feature is the polymerization or “curing reaction” taking place in situ to produce the final synthetic resin finish.

The “curing reaction” depends on a variety of factors including:

The curing is tested by assessing the floor’s moisture level and firmness. Most systems will provide a time window for how long it is likely to cure given the right conditions.

The resulting flooring can provide a seamless surface with greatly enhanced performance compared to the concrete base on which it is typically applied.

The most common types of resin floors are two-part (also called two-component) bisphenol A-based, synthetic resin systems. These are:

Other specialist chemistries available include vinyl ester, polyaspartic, and novolac resins. There are water- and solvent-based as well as solvent-free types of these synthetic resin flooring materials. All have their own characteristic advantages and disadvantages in both application and performance.

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This sludge treatment facility in Hong Kong employs a vinyl ester resin-based glass-fibre-reinforced lining system for its chemical-, thermal- and mechanical-resistance properties as well as its durability.

In general terms, all resin flooring is fast curing or hardening as well as tough and abrasion resistant. All tend to produce hardwearing finishes that are chemical-resistant to various degrees, impermeable to liquids, hygienic, and easy-to-clean. They also provide a strong permanent bond to the concrete slab.

However, there are differences between the types of resin flooring materials and product formulations on the market. The following paragraphs outline in basic terms which material is the best fit for a specific situation.

Starting at the thinner end of the scale are water-based epoxies of up to 300 microns. They are typically utilized in light to medium warehousing. These provide excellent dustproofing qualities and are a cost-effective alternative to traditional flooring materials in areas not subjected to rigorous service conditions. These types of solutions have a practical life of two to three years.

Higher build coatings of 300 to 1000 microns are ideal for use in production and processing areas due to the abrasion- and chemical-resistance properties they provide. Quartz aggregates can be incorporated into the finish to create a slip-resistant surface, which is especially useful in areas prone to wet working conditions. The practical life of such systems is three to five years.

Next on the scale are 4 to 6-mm (157 to 263-mils) thick trowel-applied epoxies. These ensure a better level of impact resistance, enabling them to withstand issues such as dropped tools and equipment, point loading from heavily-laden pallets, and the movement of forklift trucks. They are ideal for heavy industry areas (e.g. manufacturing facilities, automotive workshops, and aircraft hangars) placing a lot of demands on the floor. These systems can be specified in a decorative, multicoloured finish, and can be expected to last up to 10 years.

Thick, 4 to 9-mm (157 to 354-mils) cementitious urethane screeds represent a step up in durability and are a common sight in locations where the floor faces heavy impacts, steam cleaning, and thermal shock on a regular basis. This type of floor has anti-slip characteristics, which makes it highly beneficial in sectors such as seafood processing, dairy farming, and breweries. This is a food industry favourite and systems are available that include antibacterial additives to enhance onsite hygiene levels. This type of flooring can last 10 to 15 years even in the most intensive, heavy-duty industrial locations.

Epoxy novolac (EPN) coating systems provide significantly higher chemical- and thermal-resistance properties compared to the bisphenol A-based systems. They have a higher functionality (average reactive groups per molecule) due to switching from bisphenol A backbones to epoxy novolac precursors.

Moreover, this formulation provides the higher cross-link density needed for higher chemical resistance and thermal properties. This includes resistance to concentrated leachate, sulfuric acid, (98 per cent), sodium hydroxide (50 per cent), and biocides.

Coating systems that are 100 per cent solids epoxy novolac floor are ideal for harsh chemical- and solvent-resistant applications. In industrial plants and facilities, they are most commonly found in areas such as secondary containment, solvent storage, pump pads, tank linings, trenches, containment walls, sumps, pits, curbs, and other spaces needing protection from highly corrosive chemicals.

The types of industries that often turn to EPN flooring systems include wastewater and chemical treatment plants, the healthcare sector, electronics, power generation facilities, and textile mills.

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Epoxy novolac (EPN) resin flooring systems can withstand exposure to concentrated leachate, sulphuric acid, sodium hydroxide, and biocides, making them an attractive option for wastewater and chemical treatment plants.

EPN flooring system in action
The requirement for this type of floor was exemplified recently at the Cache Creek landfill site in rural British Columbia where 790 m2 (8500 sf) of a high-performance, 100 per cent solids epoxy novolac resin flooring system was installed.

For more than 20 years, the Cache Creek landfill site has been serving as a large transfer station for the City of Vancouver. The onsite wastewater treatment plant treats groundwater effluent as part of the ongoing post-closure care and maintenance process, which facilitates the discharge of treated water to a sanitary sewer or water body.

An epoxy novolac system was specified for use in this facility, which collects and treats effluent generated through precipitation entering the landfill as well as moisture secreted from decomposing waste material.

The aggressive chemical processes the onsite wastewater treatment plant entails meant the floor would have to withstand potential long-term contact with a number of highly corrosive substances. For example, daily operations could expose the floor to spillages of concentrated leachate, sulfuric acid, sodium hydroxide, and biocides.

Even an intermittent spillage of the highly concentrated chemicals employed onsite could lead to severe corrosion of the surface over time. Concentrated sulfuric acid, in particular, is extremely potent; this chemical is capable of corroding skin, paper, metals, and even stone in some cases.

As such, only epoxy novolac offered the chemical-resistance profile required to hold up in punishing operational conditions.

Despite the durability of resin flooring, it is important for specifiers to take a number of factors into account to ensure a long-lasting, high-performance finish.

Exposure to chemicals
Chemical abuse can come from a variety of substances, including contaminated water, grease, fuels, sanitizers, acids, lubricants, and, in certain industries, byproducts from foodstuffs such as sugars, hot oils, blood, and grease. If left unchecked, chemical attack can degrade not only the finish but can eat into the concrete substrate and affect the soil underneath.

The temperature of the chemical contaminants or harmful substances must also be considered. For example, grease is fairly inert at room temperature but highly corrosive when heated to high temperatures.

On top of this, the nature of exposure to which the floor will be subjected is also important. This is typically categorized into three degrees:

A full risk audit should provide an idea as to how many chemicals or corrosive substances a floor is likely to come into contact with throughout its lifetime. This information proves useful when it comes to specifying the flooring system for a specific location.

Additionally, chemical plants and demanding industrial facilities often have to undergo punishing clean and wash down processes involving very hot water or even steam to remove fuels, grease, and other contaminants. However, the majority of plants operate at ambient room temperatures and, therefore, during cleaning and wash down processes, floors and surfaces become subject to thermal shock as they are suddenly exposed to temperatures in excess of 180 C (356 F).

Hard floors based on epoxy, vinyl ester, or MMA chemistry are not equipped to deal with thermal shock conditions and, therefore, crack or delaminate when exposed to extreme temperature swings. This weakens the surface and invariably leads to the early onset of floor failure. Cementitious urethanes and epoxy novolac systems, however, are better equipped to survive extreme heat levels.

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An epoxy novolac system has been employed at the Cache Creek landfill site in rural British Columbia as the floor has to withstand potential long-term contact with a corrosive substances.

Substrate preparation
Getting the concrete slab or underlying substrate right is also critical to an effective chemical-resistant floor finish. Poor substrate preparation is one of the leading causes of delamination, which will occur if the concrete is too smooth, the laitance has not been removed, or there is a substance or reason for the resin coating to not effectively bond to the substrate. Delamination can cause a long list of problems for a site handling dangerous chemicals, as it will pose a safety risk and make the underlying concrete and soil vulnerable.

Similarly, the substrate’s pH levels and moisture content can wreak havoc on the floor if not addressed at the material specification stage. Concrete is, to some degree, permeable and will absorb moisture from the ground, particularly if it is low grade or located close to a high water table. Additionally, new concrete typically has a high moisture content until it fully dries out. This means the substrate’s moisture level should be thoroughly analyzed during the specification stage, and if the cyclical moisture levels are too high, then a damp proof membrane (DPM) should be applied.

Specifying the flooring system
When deciding which floor is right for the facility, it is important to discuss all the relevant factors with both a supplier and applicator with experience in creating floors in similar situations. It is also advisable to visit other facilities to see how different types of floors have stood up to comparable conditions, and if possible, install a sample within the facility to put it through its paces before committing to a complete coating. Normally, there will be a warranty for the product in question. This should always be verified with the manufacturer.

The sensitivity of resin flooring to application conditions can be considered a disadvantage. This is why it is very important to ensure the applicators are well trained in the system they are applying.

The performance of resin flooring can vary widely depending on the type of system. If one employs a thin epoxy coating in a busy industrial environment, then it will probably fail quite quickly. On the other hand, if one chooses a thick cementitious urethane, it might be fine for a long time.

It can take several days or even a week for some resin systems to fully cure, especially if the environment is cold and damp. However, it again depends on the specific system and some versions can cure in as little as two hours.

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Anti-corrosion vinyl ester resin flooring systems are a hybrid of polyester resin that have been strengthened by the addition of epoxy resin, which provides superior protection against highly concentrated and aggressive acids, alkalis, and solvents.

Applicable standards
Much of the regulation of resin flooring systems is based on International Organization for Standardization (ISO) standards—such as ISO 14486:2012, Laminate Floor Coverings, and ISO 22196, Measurement of Antibacterial Activity on Plastics and Other Non-porous Surfaces—as well as sector specific international guidelines such as Hazard Analysis and Critical Control Points (HACCP) for the food and beverage (F&B) industry.

This sludge treatment facility in Hong Kong employs a vinyl ester resin-based glass-fibre-reinforced lining system for its chemical-, thermal- and mechanical-resistance properties as well as its durability.

Epoxy novolac (EPN) resin flooring systems can withstand exposure to concentrated leachate, sulphuric acid, sodium hydroxide, and biocides, making them an attractive option for wastewater and chemical treatment plants.

An epoxy novolac system has been employed at the Cache Creek landfill site in rural British Columbia as the floor has to withstand potential long-term contact with a corrosive substances.

Anti-corrosion vinyl ester resin flooring systems are a hybrid of polyester resin that have been strengthened by the addition of epoxy resin, which provides superior protection against highly concentrated and aggressive acids, alkalis, and solvents.

Ben Smith is the managing director of Flowcrete Americas. Prior to that, he was the company’s national manager for Canada for five years. During this time, Smith increased Flowcrete’s market share, sales, and infrastructure in the region. He has more than 25 years of experience in the polymer floor and wall coatings industry. Smith has a bachelor of engineering and a master of engineering from Deakin University. He can be reached at amerweb@flowcrete.com[6].

Endnotes:
  1. [Image]: https://www.constructioncanada.net/wp-content/uploads/2018/05/Cache-Creek-Landfill-Canada-7.jpg
  2. [Image]: https://www.constructioncanada.net/wp-content/uploads/2018/05/2009-575.jpg
  3. [Image]: https://www.constructioncanada.net/wp-content/uploads/2018/05/2009-626.jpg
  4. [Image]: https://www.constructioncanada.net/wp-content/uploads/2018/05/Cache-Creek-Landfill-Canada-4.jpg
  5. [Image]: https://www.constructioncanada.net/wp-content/uploads/2018/05/T-Park-Hong-Kong-11.jpg
  6. amerweb@flowcrete.com: mailto:amerweb@flowcrete.com

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