Selection of coating thickness gauge and its influencing factors

Users can choose different thickness gauges according to the needs of measurement. Magnetic thickness gauges and eddy current thickness gauges generally measure thicknesses of 0-5 mm. These instruments are divided into probes and mainframes. The galvanized coating thickness gauges are separated from the main unit. Easy to operate, the latter is suitable for measuring non-planar shapes. Thicker dense materials should be measuring with an ultrasonic thickness gauge and measuring to a thickness of 0.7-250 mm. Electrolytic thickness gauges are suitable for measuring the thickness of gold, silver and other metals plated on very thin wires.

Dual use:

The electronic coating thickness gauge complies with the standards GB/T4956 and GB/T4957 and can be used for production inspection, acceptance inspection and quality supervision and inspection.

Instrument characteristics:

The dual-function built-in probe automatically recognizes iron-based or non-ferrous matrix materials and selects the appropriate measurement method for accurate measurement.An ergonomically designed dual display structure that reads measurement data at any measurement location.The mobile phone menu function selection method is very easy to operate.The upper and lower limits can be set. When the measurement result exceeds or meets the upper and lower limits, the instrument will give a corresponding sound or flashing light.

Extremely stable, it can be used for long periods without correction.

 Standard configuration

Coatings for the surface protection and decoration of materials, such as coatings, coatings, overlays, chemically formed films, etc., are referred to as coatings in relevant and international standards.

Coating thickness measurement has become an important part of the processing industry and surface engineering quality testing, and is the means for products to achieve superior quality standards. In order to internationalize the products, China's export commodities and foreign-related projects have clear requirements for the thickness of the coating.The coating thickness measurement methods are wedge cutting method, light intercept method, electrolysis method, thickness difference measurement method, weighing method, X-ray fluorescence method, β-ray backscattering method, capacitance method, magnetic measurement method and eddy current measurement.The first five of these methods are lossy detection, and the measurement methods are cumbersome and slow, and are more suitable for sampling inspection.The X-ray and beta-ray methods are non-contact non-destructive measurements, but the device is complicated and expensive, and the measurement range is small. Users must comply with radiation protection regulations due to radioactive sources. The X-ray method can measure extremely thin plating, double plating, and alloy plating. The beta ray method is suitable for coatings with coatings and substrates with an atomic number greater. The capacitance method is only used when thickness measurement is applied to the insulating coating of a thin conductor.With the advancement of technology, especially after the introduction of microcomputer technology in recent years, the thickness gauges are using magnetic method and eddy current method have taken a step toward micro, intelligent, multifunctional, high-precision and practical. The resolution of the measurement has reached 0.1 micron, and the precision can reach 1%, which has been greatly improved. It has a wide range of applications, wide measuring range, easy operation and low cost. It is a wide range of thickness measuring instruments used in industry and scientific research.

The non-destructive method does not damage the coating or damage the substrate, and the detection speed is fast, so that a large amount of inspection work can be carried out economically.

Influencing factor:

a base metal magnetic

The magnetic thickness measurement is affected by the magnetic change of the base metal (in practical applications, the change of the magnetic properties of the low carbon steel can be considered as slight). In order to avoid the influence of heat treatment and cold working factors, the same properties as the test base metal should be used. The standard calibrates the instrument; it can also be calibrated with the test to be coated.

b electrical properties of matrix metal

The conductivity of the base metal has an effect on the measurement, and the electrical conductivity of the base metal is related to its material composition and heat treatment method. The instrument is calibrated using a standard sheet having the same properties as the specimen base metal.

c base metal thickness
Each instrument has a critical thickness of the base metal. Above this thickness, the measurement is not affected by the thickness of the base metal. The critical thickness value of the instrument.

d edge effect
This instrument is sensitive to the steepness of the surface shape of the test piece. Therefore, it is unreliable to measure the edge of the test piece or at the inner corner.

e curvature
The curvature of the specimen has an effect on the measurement. This effect always increases significantly as the radius of curvature decreases. Therefore, measurement on the surface of the curved test piece is unreliable.

f deformation of the test piece
The probes deform the soft cover specimens, so reliable data is measured on these specimens.

g surface roughness
The surface roughness of the base metal and the cover layer has an effect on the measurement. The roughness is increased and the influence is increased. Rough surfaces can cause systematic and accidental errors, and the number of measurements should be increased at different locations for each measurement to overcome this accidental error. If the base metal is rough, it is necessary to check the zero point of the instrument on the uncoated roughness of the base metal test piece with a similar position; or dissolve the cover layer with a solution that does not corrode the base metal, and then proofread the instrument.

g magnetic field
The strong magnetic field generated by various electrical
magnetic steel ultrasonic coating gauge around it will seriously interfere with the magnetic method of thickness measurement.

h attached substance
This instrument is sensitive to adhering substances that prevent the probe from coming into close contact with the surface of the cover. Therefore, it is necessary to adhere the substance to ensure direct contact between the instrument probe and the surface of the test piece.

i probe pressure
The amount of pressure applied by the probe on the test piece affects the measurement reading, so keep the pressure constant.

j orientation of the probe
The way of the probe is placed has an effect on the measurement. In the measurement, the probe should be kept perpendicular to the surface of the specimen.

Rules to be observed:

For the eddy current method, the electrical properties of the standard sheet base metal should be similar to the electrical properties of the test piece base metal.

Check if the thickness of the base metal exceeds the critical thickness. If not, use one of the methods in 3.3 to calibrate.

c edge effect
Measurements should not be made immediately adjacent to the specimen's sudden changes, such as edges, holes, and inner corners.

d curvature
It should not be measured on the curved surface of the test piece.

e readings
Usually because each reading of the instrument is not exactly the same, several readings must be taken within each measurement area. The local difference in the thickness of the cover layer also requires multiple measurements in any given area, especially when the surface is rough.