We’d like to devote the next few blogs to the topic of commercial painting. Let’s start with a product we frequently use to paint bare metal, Sherwin Williams DTM Acrylic Coating (DTM stands for “direct to metal”).
Characteristics of an Acrylic Coating
SW DTM Acrylic Coating is a corrosion resistant paint/primer composed of 100 percent acrylic. It contains 38 percent solids by volume and 50 percent by weight. The coating is designed to be applied directly to prepared substrates:
- Iron and Steel
- Aluminum
- Galvanized metal
- Concrete/Masonry
- Drywall
- Wood
Of course, its most important feature is that it acts as both a primer and paint when applied on bare, prepared metal. It is available in gloss or semi-gloss finishes and several colors. Caution is necessary when applying to unprimed bare steel because of the possibility of pinpoint rusting — two coats are recommended, each with a thickness of 2.5 to 4 mils when dry. The coating’s acrylic polymers are water- and UV-resistant when they dry, creating a barrier against rust and corrosion.
The water-reducible (dilutable) coating has high ratings for resistance to corrosion and weathering. It received a rating of 9 on the ASTM D610 rust test and a 10 on the ASTM D714 blistering test. Most importantly, it displays superior metal adhesion, achieving more than 500 psi of pull-off strength in the ASTM D4541 test. In other words, it sticks to metal. The coating also passes tests for accelerated weathering, flexibility and resistance to moisture condensation, and has excellent durability and resistance to salt fog.
We like SW DTM Acrylic Coating because it is resistant to chemicals, dries fast (it’s dry to the touch in an hour and can be recoated in four hours), prevents flash rust/early rust, is a single-component system, has low odor, low VOCs and is easy to clean up with water. It’s a convenient timesaver because it can be applied directly to clean bare metal, although it can also be used with heavy-duty primers for extreme environments.
Application
The substrate to be coated should be dry, clean, and sound. We usually follow SSPC-SP2 protocols for cleaning: removing loose rust, mill scale, paint and other foreign substances via wire brushing, sanding, scraping, and chipping. For larger areas or poorer surfaces, we clean the substrate with power tools or blasting. You can’t use hydrocarbon solvents in conjunction with SW DTM Acrylic Coating — stick to emulsifying industrial detergents. The coating can be custom tinted before application with EnviroToner. The acceptable temperature range for application is 50° to 95°F, and humidity must be at least 5°F above the dew point, up to 85 percent.
Dark colors of the coating applied to iron and steel require a pre-coat of an acrylic primer for the greatest adhesion, durability and corrosion resistance. You have several choices for application equipment:
- Airless spray at 1,500 psi using a tip diameter of 0.017 to 0.021 inches attached to a quarter-inch hose. Reduce up to 12.5 percent with water and use a 60-mesh filter.
- Apply conventional spray using a Binks 95 gun with a 66 fluid nozzle, 63PB air nozzle, fluid pressure of 15-20 psi, atomization pressure of 50 psi, and maximum water reduction of 12.5 percent.
- Use a nylon or polyester brush, without any water reduction.
- Use a roller with 3/8-inch woven cover and solvent resistant core, without water reduction
If you are going to use a spray applicator, follow a 50 percent overlap pattern and cross-spray at right angles. You should stripe coat any welds, crevices and sharp angles for extra protection. Only proceed if rain or high humidity are not expected within a day of application. Full curing takes about a month.
PennCoat Inc. has nearly 30 years of experience providing industrial painting and commercial painting services in Pennsylvania, Maryland, New Jersey and Delaware. PennCoat also has epoxy flooring installers for all your industrial and commercial flooring needs. Contact us today to learn more about our services and the excellence we provide after nearly 3 decades of services.