Perhaps nothing affects an industrial painter’s project deadlines and cure times as much as the cold weather of the seasons. Even without massive temperature drops, however, painting contractors are always interested in ways to accelerate curing.
In this Primed Insight we offer basic principles of accelerating cure – using heat.
These are meant for contractors unable to take advantage of environmentally controlled paint booths, and need to get the job done on-site or in less than ideal facilities.
The first point that is absolutely critical is to always understand and follow the coating manufacturer’s minimum and maximum requirements for:
- Air temperature
- Coating temperature
- Substrate temperature
Most coating datasheets use 21°C / 70°F as the standard temperature for their cure rates. It’s very important to understand that a mfg’s cure speed is based the substrate’s temperature – not ambient air temperature.
Experienced painters know the folly of bringing a cold steel pipe indoors and trying to blast and paint it while it’s still as cold as the inside of a refrigerator. Huge mistake. The essential principle here is to effectively manage the substrate’s temperature before, during, and after you apply the coating. Keep it at the 21/70 mark – or hopefully much warmer! Here’s why.
There’s a common “rule of thumb” that applies to curing typical epoxies and urethanes. That rule of thumb is this.
Every 10 degree RISE in temperature from the mfg recommended substrate temperature (let’s say 21/70) will double the curing speed. Yes! Twice as fast. So 31/88 degrees will cure the paint twice as fast. 41/106 degrees will cure it 4x as fast.
Conversely, every 10 degrees DROP in temperature (from recommended substrate temperature) will half the speed. So 11/52 degrees will take twice as long as normal. 1/34 degrees will take 4x longer.
What else can be done with heat to speed up the process? Another principle that will help accelerate the cure is to warm the coating. If you can preheat the paint before applying the coating, the elevated temperature will both kick start the curing and help with flow and atomisation.