FORD FLTM BI 117-01 Thickness Measurement of Paint Films

The “FORD FLTM BI 117-01 Thickness Measurement of Paint Films” standard, developed by Ford Motor Company (FORD), describes in detail the recommended practices and equipment for measuring the thickness of paint films on metallic surfaces.

Measuring paint thickness is a method of verifying that the coating has formed as designed. The coating is designed to prevent moisture and oxygen ingress to prevent corrosion of the substrate. Therefore, the thickness of the coating has a significant impact on its functionality. This does not mean that thicker is better, but rather that the paint thickness must be sufficient to ensure the full functionality of the coating.

Paint thickness is measured using a coating thickness measurement system. There are types of non-destructive coating thickness measurement systems that use magnetic adhesion and flux exchange for measurement, and other types that use infrared and ultrasonic methods:

• Electromagnetic coating thickness gauge: The thickness of the coating can be measured by touching the surface with a probe embedded in a permanent magnet. The intensity of the generated magnetic flux varies depending on the intensity of the magnet's attractive force. This type of thickness gauge uses changes in the current passing through the electromagnet to measure the paint thickness. It can measure the thickness of the coating or coating (non-magnetic metal layer, inorganic layer or organic layer) on a magnetic metal substrate. The measuring principle is that the attractive force of the magnet embedded in the tip of the probe is proportional to the distance from the base. However, the electromagnetic coating thickness gauge cannot accurately measure the thickness of the magnetically charged paint layer.
• Eddy current coating thickness gauge: The thickness of the coating can be measured by electric current loops (eddy current) generated by electric current passing through an iron core coil (probe). The measuring principle is that the eddy current value generated on the metal surface is proportional to the distance. There are two types of eddy current coating thickness gauges: contact type, which measures the coating thickness according to the amplitude of the eddy current, and non-contact type, which measures the coating thickness according to the phase difference of the eddy currents. This gauge can be used for non-magnetic conductive metal surfaces (such as aluminum, copper and austenitic stainless steel) with a coating of plastic, resin, rubber or other insulating material.
• Infrared coating thickness gauge: Paint thickness can be measured using the spectrum obtained by illuminating infrared light onto the coating and scattering the transmitted light or reflected light. When infrared light hits the coating, absorption of light at a certain wavelength occurs depending on the material and thickness of the coating. The paint thickness of the measurement target can be calculated according to the relationship between the absorption rate and the thickness of the material used for the coating.
• Ultrasonic coating thickness gauge: When the probe touches the coating surface, the sensor transmits an ultrasonic wave to the bottom, which is reflected back to the surface. The time taken for the ultrasonic wave to be reflected is used to measure the thickness of the coating.

Commonly used conventional measurement systems such as electromagnetic coating thickness gauges and eddy current coating thickness gauges measure coating thickness based on magnetism and electric current values. Both are indirect observation methods that estimate the coating condition from the measured values, making them unsuitable for measurements in the case of multilayer coatings. Newly developed digital microscopes measure coating thickness from optical images. This microscope is not affected by light layers that require sharp focus. The images are clear and provide more information about the coating. Coating thickness, which previously could not be measured due to focusing error, is now accurately observed by capturing the actual coating condition.

Today, parallel to the development of technology, it is possible to observe three-dimensional layers of clear layers using improved focusing and multiple illumination. Thanks to the significant improvement in the camera frame rate, these devices automatically scan the focal range of the sample when the platform moves towards the observation point and instantly create a fully focused image.

Our organization has a strong staff that closely follows the developments in the world in the field of science and technology and constantly improves itself. Among the numerous test, measurement, analysis and evaluation studies provided for businesses in various sectors, there are also test services in accordance with the "FORD FLTM BI 117-01 Thickness Measurement of Paint Films" standard.