The most relevant indicator for a succesful curing of the applied prime coat in coil coating is not the air temperature of the curing oven, but the peak metal temperature (PMT). Measuring this reliably during the coating and curing processes can be quite difficult and costly. Irreversible temperature indicators provide concrete, permanent and cost-efficient proof that the strip reached the targeted temperature during cure.
Whether the metal actually reached the setpoint cannot be reliably measured from the air temperature, which is a common problem in coil coating. The solution is an irreversible temperature indicator placed directly on the coil. It records the peak metal temperature (PMT) the coil reached during coating and displays that record permanently. In combination with close monitoring of the dwell time, a temperature indicator closes the gap between what the oven reports and what PMT was actually reached.
Verifying that the coil reached the required PMT is one of the quickest objective checks you can do. Each cure spec has a certain temperature it is built for, and your coil not reaching that threshold is a valuable hint at a possible under-cure of the coat, even though it leaves no signs on the surface. An irreversible temperature indicator placed on the reverse side of the strip to be coated can display if a threshold has been exceeded and does so indefinitely.
Each chemistry has its own cure PMT window, which you can cover by using different irreversible temperature indicators with the appropriate ranges for each coating (e.g. powder cures around 150 - 200 °C and polyester at 200 - 250 °C). Simply switch indicators depending on which chemistry you are using in the current batch and you get concrete and easily readable evidence for each required PMT. If you use PVDF or fluoropolymer, which runs by far the hottest, it is covered by our reaHeat temperature indicators for extreme heat.
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