Powder coating is known for its durability and strength. It gives protection to metal, woods, as well as glass and it can hold it’s finishing maximum 20 years. Powder coating comes with a large scale of color choices. But a user can ask a question that “How thick is powder coating?” Or anyone who is thinking about using it can have the same question. The thickness of powder coating is measured:
- Before curing
- After curing
Regular measurement helps to control material cost and maintain finishing quality.
Powder coating measurement is made through the use of different methods depending upon if the test is being performed before or after powder is cured. American Society for Testing and Materials (ASTM) made a series of standards about these methods.
Now, the main question is “How thick is powder coating?”
The standard used to measure powder coating thickness is mil. A very common thickness is 6-12 mils. For your information, 1 mil is equal to 1/1000 inch.
Let’s discuss about the measurement before and after curing.
Measurement BEFORE Curing
Measuring before cure can help to find out if it needs any kind of adjustments. ASTM has some methods for it.
Rigid metal notched gauges:
In this method, a Power Comb is used for measurement. For the test, a surface is coated and then the comb is stretched through the coat. The powder thickness is placed between the highest numbered tooth which left a mark containing powder on it, and the next highest tooth which made no mark and has no trace of powder on it.
Non-contact ultrasonic instruments:
This operation requires instrument by the name of PosiTest PC Powder Checker. It is an ultrasonic instrument. It can be used on uncured powder coating to predict the thickness of cured powder coating. Its design and simple operating system allows it to work quickly and rightly. It is a non-destructive instrument. So the powder used in this test without any damage can be re-used.
Electronic coating gauges:
A conventional magnetic or eddy current coating thickness gauge is considered to perform this action. It has a powder probe which measures the thickness of powder. The probe has micro pins in amount of 3. The probe is manually pressured down on the surface to measure the thickness. This process is only applied on metal surfaces.
The Non-contact ultrasonic instruments and Electronic coating gauges method only measures the height of powder. To know the real thickness, measuring the cured powder is the best way.
Measurement After Curing
Cured powder coating is the most popular. The instruments used to measure Dry Film Thickness (DFT) are available, accessible as well as cheap, non-destructive, and smoothly operable. Some principles are used to measure different products.
- A magnetic gauge is used to measure non-magnetic coatings on steel part. Mechanical pull-off gauges generally use a permanent magnet. A force is required to pull that magnet from the coated steel surface. It can also determine the cured thickness through measuring the force. Magnetic pull-off gauges are hackly, simple, cheap, portable, and usually do not require any calibration adjustment. They are good alternative where a few reading is needed in time of production. The PosiTest FM is an example of it. It has tolerance of ±5%. Another example is PosiPen. It is used to get pin-point result on small parts. It can handle temperature up to maximum 230 degree Celsius. It has tolerance of ±10%.
- For non-metal products, an ultrasonic principle is used. Ultrasonic testing is used by sending ultrasonic wave into coating with a probe. PosiTector 200 B Std is an ideal model for measuring powder coating thickness on non-metal product like wood and glass. The range it possesses contains maximum 40 mils.
- An eddy current principle is used providing the coating non-conductive closed loops within conductors.
The instruments used in this principle has tolerance between ±1 and 3%.
To know the answer of “How thick is powder coating?” we had to know many things. But the powder coating gives us protection for many years. So, knowing these things are necessary and good for us. You should check your powder coating regularly. It will be good for your products and will also save your money. Let us know if you have any question.