Spraying blue paint on a gray part

March 2015

When deciding on a quality topcoat, you may come across the option between Alkyd and Urethane. Both can fit your need when expected performance is understood along with your budget.

 

So, what is the real difference?

 

First, we can examine speed of how each topcoat cures…

 

Alkyds are typically one component (no hardener added) and will be slower to fully dry. They use the oxygen in the air to complete a reaction that changes the coating from wet-flowing to hard and durable. It takes longer for the oxygen to disperse throughout the film, so dry times will be extended if you accidentally spray thicker than recommended.

 

Urethanes are typically two component (needs an isocyanate hardener) and quicker to cure. Urethanes do not depend on oxygen dispersion throughout the film, because the two reactants are already mixed throughout the wet coating. The resin and isocyanate meet, react, and create a very durable polyurethane coating as they proceed to dry quickly.

 

Next we can compare relative performance…

 

This is best described as “Alkyd is better and Urethane is best.” Alkyd coating is a very good choice for industrial and low-end transportation applications. Urethanes are used on high-end trucks, buses, trailers, and automobiles.

 

Finally, along with these variables come relative differences in price. Alkyds tend to be less expensive than Urethanes.

 

Ultimately, both work very well for their intended purpose.

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