[Thickness measurement dry goods] How to measure the thickness of metal materials through the paint layer?

through lacquer or other similar coatings,

Measuring Remaining Wall Thicknesses

There are two solutions to this problem:

Echo-to-echo measurements and through-coat measurements
.

Due to their excellent detection of rough surfaces and pitting defects, dual element probes have long been the standard industrial equipment used in corrosion measurement applications
.
Therefore, users are generally advised to use these probes for all common corrosion thickness measurement applications
.
In some applications, such as the inspection of metallic materials with smooth paint layers, the user may be advised to use a single element retardation block probe due to the need for higher measurement accuracy
.


Theoretical

Echo-to-echo thickness measurement is a well-established technique that simply measures the travel time of an acoustic wave between two consecutive backwall echoes
.
The two consecutive back-wall echoes represent the two consecutive round-trip sound paths completed by the sound wave propagating in the material under test
.
When measuring metal materials with paint layers, these multiple back-wall echoes only occur inside the metal, not on the paint layer, so the period between each pair of adjacent echoes (eg: back-wall echoes 1 to 2 , backside echoes 2 to 3, etc.
) only represent the thickness of the metal, not the thickness of the paint layer
.

Through-coating measurements use a patented software method to identify the time period represented by the round-trip sound path of the sound beam in the paint
.
This time period is used to calculate the coating thickness and display the coating thickness on the instrument's screen
.
By subtracting this time period from the overall thickness measurement, the thickness gauge can also calculate the thickness of the metal and display it on the screen
.

Advantages of both techniques Advantages of the

The Through Coating feature uses the D7906-SM or D7908 probe and can only measure non-metallic coatings such as paint or epoxy materials 0.

Metal thicknesses that can be measured in through-coat mode typically range from about 1 mm (0.

Echo-to-echo measurement range

In echo-to-echo mode, the measurable thickness range depends on the probe selected and the type of thickness gage used, as well as the acoustic properties of the metal being measured and the condition of the surface being measured

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