Secondary containment coatings for storage of hazardous materials such as flammable solvents, corrosive liquids are required by state and local laws to mitigate damage from accidental spills and/or natural disasters of flood, fire and earthquake.
Demands for the coating and containment will vary by governing bodies and locations of the storage site. Typically, a containment area would need to hold spillage of all product in the area for 24 hours without leakage into the ground water and surrounding area. Epoxy coatings of the self-leveling type with higher elongation and flexibility facilitates good crack bridging properties under static conditions and low temperature.
EC-422A, with its backbone of a highly flexible amine component and good chemical resistance, is ideal for these situations.
Epoxies, by their makeup, have good chemical resistance to many solvents, acids and bases. Certain solvents and acids such as ketones and organic acids can be problematic for extended exposure. In these areas, it’s best to use a Mannic base type of curing agent that does not contain plasticizers. ED-122R is a Mannic base type curative incorporating a substituted Phenolic material and is plasticizer free. Its rapid cure properties require good handling and small batch mixers on the job site. Kitchen flooring beneath deep fryer equipment is a key area to use this special curative in the floor system.
Two part epoxy emulsion systems that use white pigments such as TiO2 and carbon blacks to develop gray floor coatings suffer typically from pigment flood-float.
These pigments, in particular, require additives to keep the pigment mix from separation in the container and on the floor during the drying times.
Sepiolite clay is an excellent anti-float additive which imports the proper charge to a dispersion to prevent the natural tendency of these pigments to separate.
The sepiolite structure has internal channels open to the surface. Their action with polar solvents, such as water, creates a three dimensional network. This provides excellent suspension of the pigment particles. Hi-purity sepiolite act as thickeners to the emulsions with outstanding suspension and anti-sagging properties. Reduction of synthetic thickener use is therefore, an additional benefit.
The excellent properties of epoxy coatings relative to corrosion protection make them the polymer type of choice in many applications. They wet metal surfaces very well and show a tolerance to water and humidity. 2K
Epoxy coatings employing a modified cycloaliphatic amine such as EC 423 will cure on a substrate in the presence of water and high humidity. The basis for good wet adhesion is due to the high rigidity of the thermoset epoxy and the bonding groups of the binder network interacting with the substrate surface. The interaction withstands under creepage of water to provide a lateral barrier effect.
The excellent wet adhesion and corrosion protection of epoxy coatings exhibit themselves in thin primer coatings as well.
Since the gel point of the 2K epoxy coating is reached only after an extensive crosslinking period, most of the volume shrinkage occurs during this time. Any remaining shrinkage after the cure period is not critical.
Epoxy coatings are free of internal stress due to this cure cycle phenomenon. This cure process accounts for the outstanding adhesion compared to other binder systems.
Epoxy coatings are further enhanced by anti-corrosive pigments such as Zinc Phosphate and barrier pigments such as Micaceous Iron Oxide and Mica.
Two part solvent less Epoxy Coatings based on Bis A or Bis F epoxy resin (EEW190 type) and a modified cycloaliphatic amine of the 1,3 BAC type (Epoxycure 423) are an excellent starting point for these systems.
Hydrostatic pressure in concrete floors can be caused by, in the case of newly poured concrete, the cement hydration reaction.
Water vapor transmission (WVT) in existing or old concrete may originate from temperature and humidity differences inside the concrete and room space above.
Wet conditions below ground level can cause a hydrostatic head. Forcing water vapor up through the pores of the concrete and cause blistering to a coating.
A two-pack (Epoxy Resin\Amine) solvent-free Epoxy is, by itself, a very good vapor barrier coating (.4 grams MVT) then can be further reduced by the additional of the Platey Mineral Fillers. These products arrange in a platey pattern with each other in the epoxy coating and provide an additional moisture barrier and reduce the MVT rate below .2. These products are used at low levels with very good effect.
EC 422A and EC 423 offer the formulator range of cure times, low application viscosities and through cure times permitting a good return to service window. The cure profile of EC 423 in particular, assures a water barrier in high humidity conditions of summer applications. These are gained at the sacrifice of work life but this can be handled by smaller mixes on the job site.