TESTING & MEASUREMENT
Measuring Duplex Coatings in the Automotive Industry For automotive manufacturers, it is of increasing importance to control the quality of the paint processes in order to ensure effective corrosion protection while reducing costs. Especially in EDP (electrophoretic deposition) processes, this requires adherence to tight tolerance limits, which in turn, requires careful monitoring. But the measurement task itself should also be fast and cost-effective; the instrument must be able to measure lacquer atop various base materials (mainly galvanized steel or aluminium) without refitting or recalibration. To measure lacquer coatings on both steel and aluminium with the same instrument and without having to change probes, it is necessary to utilize different methods. Furthermore, when the steel is galvanized, the Zn coating must be measured separately in order to determine the thickness of the lacquer coating above it. Especially for this purpose, FISCHER has developed the PHASCOPE® PMP10 DUPLEX and the ESG20 probe, unifying three measurement methods in one system for testing the thickness of each layer precisely and accurately.
For a typical lacquer/ Zn/Fe combination, the Zn layer is measured through the lacquer using the phase sensitive eddy current method (employing lift-offcompensation). At the same time, the overall coating Typical measurement tasks in the automotive industry. MS = magnetic induction thickness (Zn+ method, WS PS = phase sensitive eddy current method, WS AS = amplitude lacquer) is measured sensitive eddy current method. using the magnetic induction method; must be met in order to ensure the minimum the thickness of each thickness for effective corrosion protection individual layer is derived from this and displayed on the instrument. while minimising the amount of material consumed. This is why it is necessary to For coating systems on aluminium, the measure the Zn layer underneath the paint to amplitude sensitive eddy current method is determine the real thickness of the lacquer, used. A special conductivity compensation since even minor variations in the Zn coating feature ensures that the various conductivities could erroneously indicate a (non-existent) of different Al alloys exert no influence on the flaw in the paint process. measurement of the lacquer layer. Without any additional calibration, the coating thickness can be measured precisely and reproducibly in one pass even when the substrate changes, as the probe automatically identifies what the base material is. Typical measurement tasks in the automotive industry. MS = magnetic induction method, WS PS = phase sensitive eddy current method, WS AS = amplitude sensitive eddy current method. Especially with costly EDP coatings, very small tolerances – often of just ± 2 µm –
PHASCOPE® PMP10 DUPLEX
32
MAY 2022
The PHASCOPE® PMP10 DUPLEX, together with the ESG20 probe, was developed specially to meet the requirements of the automotive industry. Its three different measurement methods make it possible to measure lacquer coatings precisely, in one operation, whether on galvanized steel or on aluminium. Your local FISCHER representative will gladly provide you with further information. Telephone: +44 (0)1386 577370 Email: mail@fischergb.co.uk Visit: https://fischerinstrumentation.co.uk/
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