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Coating Thickness Measuring / Film thickness gauges

Definition

The coating thickness measurement deals with the determination of the layer thickness of coatings and coatings on surfaces. As a layer thickness is generally referred to the thickness of a coating, e.g. paint, which is firmly applied to a base material. This coating can be a single coat or a multiple coat (zinc on steel). You will know the instruments also as film thickness measurement device, coating thickness gage, paint coat meter or generally paint gauges.

Coating Thickness Meters

Basically: Substrate made of metal

Most important requirement: There is a metallic substrate. Coating thickness measurement over ceramic, glass or plastic is not possible with our devices.

"FE" metals and "NFE" metals

FE means "ferromagnetic". FE metals are magnetizable: steel, iron, cobalt, nickel.
Nickel is a special case because coatings of chemical nickel contain phosphorus and are not ferromagnetic from 11% Phosphor-content

NFEs are the "non-ferromagnetic" metals that are electrically conductive. For example, aluminum, copper, zinc or stainless steel.
Another special case: even stainless steel can be ferromagnetic (in the case of a ferritic alloy).

Coating Thickness Meters

Examples of the use of coating thickness gauges

Paint thickness measurement

Quality assurance in the painting process

  • Compliance with minimum paint thickness
  • Measure paint thickness for optimization of material usage

Authorized car experts

  • Thickness checking gauge: Is the paint original or repainted after an accident?

Coating thickness measurement in electroplating and anodizing

Quality assurance with galvanic coating

  • Galvanizing, chrome plating on steel
  • Lacquered galvanizing, zinc and lacquer thickness measurement of both layer thicknesses (zinc and lacquer)
  • Copper coated steel gravure rolls

Quality assurance in anodizing aluminum coatings

Quality assurance for rubber coatings of metal, rubber coating measurement

Coating Thickness Meters

What are the requirements to be able to measure the layer thickness ?

  • The layer must be dry and cured.
  • The coating must not fall into the same group (FE, NFE) as the substrate.
  • Strong magnetic base material can disturb the probe so that it is internally damaged.
  • Thin layers of less than 3 μm can't be measured stably.
  • The base material must not be thinner than 0.5 mm.
  • For small contact surfaces of less than radius 2mm (FE) or 6mm (NFE), the probe can’t be positioned.
  • With a domed base under an outer radius / convex of 2mm (FE) or 6mm (NFE) as well as under an inner radius / concave of 8mm (FE) or 38mm (NFE) is also not attachable.

Coating Thickness Meters

Multilayer structure

In multilayer constructions, two layers can be measured separately if
  • the substrate is ferromagnetic,
  • the first layer is metallically non-ferromagnetic above the substrate, and
  • the topmost layer is non-conductive, for example paint or rubber.

Coating Thickness Meters

Further restrictions

Roughness

For a rough layer it is necessary to measure in several places and to look at the result statistically (minimum, maximum, mean value). MEGA-CHECK Master can take over this task. They move the probe over the surface and automatically determine statistical values.

Hard to reach measuring points

The swiveling probes of TOP-CHECK or MEGA-CHECK allow to measure at an angle of up to 90°.

Measuring in pipes

For tubes or narrow openings there are special probes such as PF-1T, PF-2T or PF-3T.
The pipe itself must not be too narrow, the measurement is disturbed in narrow pipes by reflection.

Environmental conditions

  • Not at temperatures below 0 ° C due to electronics
  • Not at temperatures above 50 ° C, the probe could be damaged
  • Do not measure with eddy current method under water, as water itself is conductive

Coating Thickness Meters

 

Coating Thickness Meters

Technique excursus: what is eddy current, what is magnetic inductive

List-Magnetik devices use two of the non-destructive testing (NDT) techniques, the ISO 2178 magnetic induction process and the ISO 2360 eddy current process. The magnetic induction process is used when the substrate itself is magnetizable (steel or iron). Here we use magnetic paint thickness gauges. The eddy current method comes into play when the substrate is at least electrically conductive (other metals such as aluminum).

Coating Thickness Meters

Calibrate the device

List-Magnetik devices are factory calibrated and do not necessarily need to be calibrated by the user. An exception is when measuring on curved surfaces or on different base materials. Here, according to ISO 2178, a two-point calibration should be performed on an uncoated same object.

Coating Thickness Meters