Waterbourne
Moderate Cracking
Low Severity Cracking
Waterbourne
This paint is specified by Federal Specification TT-P-1952D, the U.S. government standard for latex (acrylic) paint. Like most latex/acrylic paint, it involves a pigment combined with an acrylic (plastic) binder and carried in a water vehicle, thus the name “waterbourne”. It uses ammonia and methanol as drying agents. It can dry to a track-free state in 2-15 minutes but requires 24-48 hours to fully cure. It comes in two basic types depending upon curing conditions:
- Type I. Used for normal weather curing conditions, which P-620 defines as 50 percent relative humidity, moderate temperatures and slight breezes.
- Type II. Used for adverse curing conditions, which P-620 defines as night striping, higher humidity (around 80 percent), low air movement and lower surface temperatures down to 12°C (55°F).
Advantages of waterbourne paint:
- Relatively low cost when compared to epoxy or MMA markings.
- It is a non-hazardous material. It contains virtually no volatile organic compounds (VOC) and cleans up with water. Thus, disposal and cleaning is simple and relatively environmentally friendly.
- Highest coverage rate (115 ft2/gallon) requires less time and paint.
Issues with waterbourne paint:
- Can potentially react with iron sulfide in HMA aggregate causing discoloration. It may be possible to add a rust inhibitor to the paint, however this solution is unproven.
- Applied over a new HMA surface, the paint may discolor to a golden brown. It is likely that this discoloration will disappear over a short period of time, often assisted by rain.
- Paint could bond to the HMA surface better than HMA bonds to itself. This could lead to cracks along the edges of the paint markings (see Images) as the paint expands and contracts with temperature changes.