Chemically resistant linings and coatings are an integral part of many industries. They are designed to protect surfaces from corrosion and degradation, thereby extending their lifetimes.
Chemical resistance in this context is defined as the capacity to protect the underlying substrate (e.g concrete, mortar or an equivalent) from chemical attack, corrosion, water ingress or abrasion.
They are typically applied to various containment systems, such as:
- Primary containment systems (e.g. the inner surfaces of above-ground storage tanks)
- Secondary containment systems (e.g. bund walls and bund floors)
These are resin-based systems, which are industry standard for small-to-medium-sized bunds, where they deliver superior performance to materials used at a larger scale.
Please note that there is no ‘one size fits all’ for chemically resistant coverings. This is also true for individual categories of chemicals – like acids, where a single type of lining does not adequately provide resistance across all acid types, but rather a certain few. This is particularly evident when considering systems to contain more concentrated or harsher chemicals.
In response, manufacturers have generated more bespoke resin systems tailored toward more aggressive chemicals.
The table below provides examples of lining systems (with and without reinforcement) that are designed to provide chemical resistance to a range of substances that would otherwise cause an accelerated breakdown of the base structure.
| Epoxy | Polyester | Vinyl Ester | Polyurethane | |||
|---|---|---|---|---|---|---|
| Test @ 22oC | Test @ 15oC | Test @66 oC | Test @ 15oC | Test @71 oC | Test @ 22oC | |
| Acetic Acid (20%) | R | R | R | R | R | R |
| Acetic Acid 25-50% | - | R | NR | R | R | - |
| Acetone | NR | - | - | R | NR | NR |
| Alcohol - Isopropyl (10%) | - | - | - | R | max 66 | - |
| Alcohol - Isopropyl (100%) | R | NR | NR | R | NR | - |
| Aluminum Chloride | R | R | R - max 51 | - | - | - |
| Aluminum Sulfate | R | - | R | R | - | |
| Ammonia 10% | R | - | R | R - max 38 | - | |
| Ammonium Chloride | R | - | R | R | - | |
| Ammonium Hydroxide | R | R | NR | R | max 49 | - |
| Ammonium Nitrate | R | NR | NR | - | ||
| Ammonium Phosphate | R | R | R | R | R | - |
| Ammonium Phosphate | R | NR | NR | - | - | - |
| Ammonium Sulfate | R | R | R | - | - | - |
| Beer | R | R | NR | R | R | |
| Benzene | - | - | - | - | - | NR |
| Boric acid | R | - | - | R | R | |
| Bromine | NR | - | - | R | NR | |
| Butanol | - | - | - | - | - | NR |
| Chlorine Water | - | NR | NR | - | - | - |
| Chromium Sulfate | - | R | R | - | - | - |
| Citric Acid | R | R | R | R | - | |
| Chlorine Water | - | - | - | R | R | - |
| Chloroform | - | - | - | - | - | NR |
| Chromic Acid 20% | - | - | - | R | R - max 49 | NR |
| Copper Chloride | - | R | R | - | ||
| Copper Nitrate | - | R | R | - | ||
| Copper Sulfate | - | R | R | - | ||
| Diesel Fuel | R | R | NR | R | R | R |
| Ethanol | - | R | ||||
| Ethylene glycol | R | R | R | - | ||
| Formaldehyde, 40% | R | R | NR | R | R - max 66 | R |
| Formic Acid | R | R | NR | R | R | NR |
| Fuel Oil | - | R | NR | R | R | - |
| Hexane | R | R | NR | R | R | - |
| Hydraulic Fluid | R | R | NR | R | R | - |
| Hydrobromic Acid, 100% | NR | R | NR | - | - | - |
| Hydrochloric acid, 20% | R | - | - | - | - | NR |
| Hydrofluoric Acid, 75% | R | - | - | R | R - max 66 | - |
| Hydrogen Peroxide, 10% | R | R | R - max 49 | R | R - max 49 | - |
| Hydrogen Sulfide | R | - | - | R | R | - |
| Isopropanol | - | - | - | - | - | NR |
| Jet Fuel | R | R | R | R | ||
| Kerosene | R | R | R - max 49 | R | R | R |
| Lactic Acid | R | R | R - max 93 | R | R | R |
| Lithium Bromide | - | - | - | R | R | - |
| Magnesium Chloride | - | - | - | R | R | - |
| Maleic Acid | R | - | - | R | R | - |
| Methanol | - | - | - | R | R | R |
| Methyl Ethyl Ketone | R | - | - | NR | NR | - |
| Motor Oil | - | - | - | R | R | - |
| Naphtha | R | R | R - max 100 | R | R | - |
| Nitric Acid | NR | R | NR | R | R | NR |
| Nitric Acid 20% | - | - | - | R | R - max 49 | - |
| Oleic acid | R | R | R | - | - | - |
| Oxalic Acid | R | R | R | - | - | - |
| Petroleum | - | - | - | - | - | R |
| Phosphoric Acid | R | R | NR | R | R | NR |
| Potassium Chloride | R | - | - | - | - | - |
| Potassium Hydroxide | R | - | - | R | max 66 | - |
| Potassium Nitrate | R | R | R | R | ||
| Potassium Sulfate | R | R | R | R | R | - |
| Sodium Acetate | R | R | NR | R | R | - |
| Sodium Hydroxide, 50% | R | R | NR | R | R - max 61 | - |
| Sulfuric Acid 0-50% | - | R | - | R | R | R |
| Sulfuric Acid, 0-100% | R | NR | - | R | R | - |
| Toluene | R | NR | R | R | R | NR |
| Urea | R | R | NR | R | R - max 49 | - |
| Vegetable Oils | R | R | - | R | R - max 38 | R |
| Vinegar | R | R | NR | R | R | R |
| Water - Deionized | R | R | NR | R | R - max 61 | R |
| Water - Demineralized | R | R | R | R | R | R |
| Water - Distilled | R | R | R | R | NR | R |
| Water - Fresh | R | R | R | R | R - max 60 | R |
| Water - Salt/Sea | R | R | R | R | R | R |
| Xylene | R | NR | R | R | R | - |
Resistance is not the only consideration. Linings should also perform at elevated temperatures and demonstrate good abrasion resistance.
Surface Preparation
The surface should then be subjected to an abrasive method to remove dirt, dust, and debris. Afterwards, residual dust should be removed with a vacuum or brush. Finally, the surface should be rinsed with clean water to ensure all contaminants have been removed. Once the surface is clean and dry, a chemically resistant covering can be applied.
Note: typically, a primer is applied to the surface to 1) facilitate and maximise adhesion and 2) to act as a moisture-curing blocking agent to prevent liquids from contacting the base of the lining via the substrate.
Polyester
Used alone, polyester resin is brittle, yet when combined with glass fibre matting it forms a high-performance material ideal for chemical containment. An MEKP catalyst is added to polyester resin to initiate the curing reaction. Whilst this is ongoing, the mixture is applied to pre-positioned glass fibre matting. The result is a fibreglass composite covering, which acts as a seamless barrier to external stressors.
Epoxy
An epoxy resin system is a two-part system that is mixed together in a specific ratio and applied to the desired surface. The first part is the epoxy resin, and the second part is the hardener. Typically, a primer will be applied first prior to the epoxy system. Thereafter, a topcoat layer will be applied.
Vinyl Ester
Vinyl ester resin is also catalysed prior to application. It is combined with a glass fibre reinforcement to add a structural backbone and for chemical containment applications also includes a protective veil. This system is applied to a primer-coated surface and is coated with a final layer of vinyl ester-based topcoat. Vinyl ester resins are a certain form of polyester resin. In addition to their enhanced chemical resistance, they offer improved strength making them ideal for demanding industrial environments. Vinyl esters are typically produced when epoxy resin reacts with methacrylic acid.
Data obtained experimentally in the table above highlights the benefits of vinyl ester resin systems.
Polyurethane
Polyurethane resin is then mixed with a catalyst and applied to the surface using a roller or squeegee. The surface is then allowed to dry completely over a period of several hours before it is ready to use. Polyurethane has several benefits centring on its versatility and flexibility. However, it has limited chemical resistance when compared to vinyl ester systems and is susceptible to damage.
Frequently Asked Questions (FAQs)
Q. What is the difference between a chemically resistant lining and coating?
A. Chemically resistant linings and coatings are surface coverings that are resistant to chemicals. This type of lining is often used in industrial applications where chemicals are present. A lining = the covering inside of a structure (e.g. storage tank) and a coating = the covering outside of a structure (e.g. a flat roof membrane).
More detail is described here regarding differences between linings and coatings.
Q. What are some common chemicals that a chemically resistant lining can resist?
A. Some common chemicals that a chemically resistant lining can resist include acids, bases, and solvents. The extent of resistance is dependent on the resins used.
Q. What are some common applications for a chemically resistant lining?
A. Some common applications for chemically resistant linings include storage tanks, bunds and gullies at chemical processing, wastewater treatment, and fuel storage plants.