Polyester Powder Coatings – TGIC, TGIC-Free, HAA, & Primid Explained

Polyester powder coating technology has been around since the 1970s and accounts for 30-45 percent of powder coating product sales globally. There are two main categories of polyester powder coatings used in the industry today: TGIC (an acronym for the chemical compound curing agent it uses, triglycidyl isocyanurate), and HAA. HAA polyester powder coating uses β-hydroxyalkyl amides as its curing agent and is often called TGIC-free or Primid polyester powder coating after the brand of curative used in most HAA powder coatings. While both categories of polyester powder coatings perform relatively similarly, there are some pros and cons that can tilt a company toward one or the other. 

TGIC coatings typically offer better chemical resistance and corrosion resistance than their TGIC-free counterpart. The HAA curing mechanism can release water, which makes the coating slightly more water soluble than TGIC-polyester. Because of its slight water-solubility, HAA coatings are more susceptible to acidic and alkaline chemicals. All of this makes HAA-polyester less corrosion resistant than TGIC-polyester.  However, with different formulations, a Primid polyester coating can perform on par with TGIC. When it comes to impact and abrasion resistance, flexibility, and hardness, TGIC and TGIC-free polyester powder coatings are the same. 

For application and curing, TGIC-polyester cures at a lower temperature than HAA-polyester (roughly 290 degrees Fahrenheit and 330 degrees Fahrenheit respectively). Many companies find HAA-polyester applies more easily and sticks to nooks and crannies better than TGIC-polyester. Thickness of application varies greatly between the two, with TGIC-polyester coating able to reach about 10 mils (250 microns) thickness and HAA-polyester coating reaching 3.5 – 4.0 mils (90-100 microns) thickness. When it comes to color stability, TGIC-polyester comes out ahead. HAA-polyester can yellow in color in overbake conditions, while TGIC-polyester has very little color drift over a wide range of cure times and temperatures.