What Does Amine Sweat Mean?
Amine sweat is a thin, sticky and shimmering film or layer of the organic compound amine carbamate on the surface of epoxy coatings and fillers. It is formed when some amine curing agents co-react with carbon dioxide and water, as it is exposed to high humidity, moisture or low temperature while curing and sometimes even after complete epoxy curing.
Amine sweat, which seems to be changing colors like an opal, may also appear as a dull grey or white layer; sometimes it’s hardly visible.
Other terms for amine sweat are: “amine blush”, “amine sweat”, “amine bloom” and “amine carbamate”.
Corrosionpedia Explains Amine Sweat
Amine sweat in epoxy coating is an indication of any or all of the following: incorrect choice of coating material and/or exposure of uncured epoxy surface to an environment with high humidity and temperature at dew point. However, with the right choice of coating material, amine sweat will not be a problem within a wider range of environmental conditions.
Coating over amine sweat or amine blush can result in yellowing or other shades of discoloration, gradual loss of glossy finish, and poor adhesion with overcoats. Removing amine sweat means additional time and cost to the project.
Amine Sweat Removal
Amine sweat in uncured epoxy is mostly water soluble. However, washing it with water still requires pressurized application, surface scrubbing or, in some cases, detergent and hot water. Solvents or thinners can also be used as well as sanding and other manufacturer-recommended methods.
Factors to consider in choosing the right coating material to avoid amine sweat
- Type of curing agent: Manufacturers have developed curing agents or hardeners that are less hygroscopic and are not likely to form amine sweat like the aliphatic amines, polyamide and other low molecular weight amines.
- Accelerators: Amine sweat is less likely to be produced with the fast curing of the coating mixture. However, users should be aware that accelerators, commonly the tertiary amines, would reduce the pot life of the coating mixture.
- Creating correct curing conditions: Using hot air blowers, industrial dehumidifiers may help create the correct curing conditions for internal applications.
- Thorough mixing of hardener with other components: This advances the polymerization or curing process, and reduces the chance for the curing agent to react with carbon dioxide and water to form amine sweat.