Coating: Epoxy-based
Description
Note: record in progress
A high-performance resin and hardener mixture that forms a tough, seamless, and bonded finish. Epoxy-based coatings start with two main components: a resin and a hardener – often referred to as Part A and Part B. When these two substances are mixed together, they form a strong bond that is resistant to both physical and chemical damage producing coatings that are widely used in industrial settings. For two part epoxy systems, the drawbacks are that preparation requires care and attention to details. Any substrate must be clean and dry; application over a previous coating is not recommended. Following mixing instructions, cure times and environmental conditions are all critical to obtain a successful coating.
Table 1. Comparison of four primary types of two-component epoxies (based on information from Sherwin Williams Epoxy Guide)
| Epoxy | Description | Advantages | Disadvantage | Applications |
|---|---|---|---|---|
| Amine epoxy | Form very hard, adherent films with excellent chemical and corrosion resistance. Amine cured epoxies are often used as protective coatings and linings in highly corrosive environments. Amine epoxies require care in handling since the amines can be moderately irritating to the skin, and may cause allergic reactions. | Very good chemical, water and solvent resistance; forms hard, abrasion resistant film, excellent corrosion resistance; good vapor barrier | Amines can be irritationg/toxic; relatively short pot life and recoat time; slower dry times than polyamides; may discolor and/or chalk | Barrier coating, liquid storage tanks, structural steel, bridges; off shore structures |
| Polyamide epoxy | Polyamide epoxies generally offer the widest latitude in coating formulation. They are considered more resilient and flexible, and have better weathering resistance and a longer pot life than amine cured epoxies. Polyamide epoxies generally have less solvent and acid resistance than amine cured epoxies. | Very good chemical and. Water resistance. Longer pot life tha amines, easy to apply, dures more quickly thatn amine, good weathering and film flexibility excellent adhesion | High viscosity, temeprature dependant, faster dry than amines, slow cure, chalks | Water immersion, offshore structures, storage tanks, waste water plants, structural steel, bridges |
| Amidoamine epoxy | Amidoamines are reaction products of a polyamine and a fatty acid. Their properties generally fall between those of amines and polyamides. They have good water and corrosion resistance like amines, and good toughness like polyamides. They have relatively small molecular size giving them low viscosities and making them very good surface wetters. | Excellent surface wetting and adhesion, excellent water resistance, low viscosity, longer pot life than amines, good gloss retention | temperature dependant, slow cure, fair color retention | Barrier coating for vapors, general industrial, bridges |
| Epoxy Phenolics/Novolacs | These coatings allow wide range formulating latitude. Novolac epoxy resin increases chemical resistance and solvent resistance. Increasing the level of phenolic increases the chemical and solvent resistance, but the coating loses flexibility. Some phenolics require heat curing. | High heat resistance, excellent chemical and solvent resistance, excellent corrosion resistance, hard, abrasion resistant film | some may require heat cure, slow air cure, relatively brittle, may discolor and/or chalk | Chemical resistance, tank lining, containment, bgeneral industrial, ridges |
Other epoxy coating formulations allow one-step applications both as liquid and solid resins.
- Epoxy acrylic hybrid systems are used as coatings for household applications, e.g., indoor and outdoor furniture and metal products.
- Waterborne epoxy coatings are dispersions of special formulations of the resins with suitable surfactants and can be applied by electrodeposition techniques.
- Epoxide resins can be applied as powders using fluidized bed techniques.
Commercial Products
The following names for commercially available Epoxy Coatings were pulled from the AIC Materials Testing page (search for coating and epoxy)
- Tnemec Company: Enviro-pox Series 287 Epoxy Floor Coating (2019)
- Cur-a-flex: Elast-o-coat (medium gray) Resin and Hardener (2019)
Risks
- improperly prepared coatings can peel or crack
Physical and Chemical Properties
- Very corrosion resistant
- Very durable for high traffic, indoor areas; easy to clean
- Highly resistant to oils, chemicals, solvents and water
- Produces a seamless surface that is impenetrable by liquids
- Can be slippery when wet
- Yellow, fades or chalks when exposed to UV light
- Very rigid and brittle; not recommended for flexible surfaces like wood
Resources and Citations
- Sherwin-Williams: Epoxy Coatings Guide
- Science Direct: [
- Runyon Surface Prep: Pros and Cons of Epoxy Coatings
- Leggari: Epoxy Flooring Pros and Cons