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January 25 - January 29, 2021

Is there any problem measuring the DFT of an MIO coating using an electromagnetic induction gauge?

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DFT can be measured just like normal coating using electro-magnetic gauge. as MIO coatings are usually not magnetic.

From Bryant Chandler of Greenman-Pedersen, Inc. on February 5, 2021:
If you or a client have concerns about DFT testing of a MIO coating system take some panels, blasted or unblasted and mask off a small portion then apply the MIO to the blasted steel. Remove the masking, measure accurately the thickness of the uncoated and coated portions, subtract the two readings which give you the coating thickness than measure the coated portion with a DFT gage. Compare The two readings. If using blasted panels be sure to account for the BMR when using the DFT gage since the first set of measurements using a micrometer does not account for the BMR.

From Rob Francis of R A Francis Consulting on January 25, 2021:
I think the Australian Standard AS3894.3 is the only one that says anything about MIO - "The magnetic effect of certain pigments and extenders, such as micaceous iron oxide (MIO) and red iron oxide, can affect the accuracy of measurements obtained from some instruments. NOTE: Such errors are usually within the normal accuracy of the instrument and may not be significant." (Clause 5(k)). However, some work carried out in Melbourne by Ted Riding (unpublished) suggested that MIO can make a difference at high levels (>25%) and a special adjustment method should be used with electromagnetic induction gauges. Fortunately, such levels of MIO give low rather than high readings so you are likely to have over rather than under thickness, which is unlikely to be a major problem (other than additional cost of paint!).

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Tagged categories: Asia Pacific; Coating Application; Dry Film Thickness (DFT); EMEA (Europe, Middle East and Africa); Latin America; North America

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