M00001116
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ISO 19840 2nd Edition, September 1, 2012 Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Measurement of, and acceptance criteria for, the thickness of dry films on rough surfaces
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Availability date: 07/13/2021
Description / Abstract:
This International Standard specifies a procedure for the
verification of dry-film thickness against nominal dryfilm
thickness on rough surfaces, including the adjustment of the
instruments used, the definition of inspection areas, sampling
plans, measurement methods and acceptance/rejection criteria.
For the purposes of this standard, any specified thickness is
taken to be nominal as defined in ISO 12944-5, and the dry-film
thickness is the typical thickness above the peaks of the surface
profile.
The procedure described in this International Standard is based
on the use of instruments of the permanent magnet, electromagnet
and eddy current type. Instrument accuracy is verified both at zero
and at a known thickness on a smooth surface and adjusted if
necessary.
Measurements taken on a coating on a roughened steel substrate
will therefore be higher than the actual value above the peaks of
the profile. The thickness of the dry film above the peaks of the
profile is defined as the instrument reading minus an appropriate
correction value.
The dry-film thickness is obtained by using the appropriate
correction value applied to readings based on adjustment on a
smooth, flat steel surface.
Where individual readings, based on adjustment on a smooth, flat
steel surface without the use of correction values, are specified
or agreed, it is important to recognize that this method does not
conform with this International Standard.
This standard is applicable if the nominal dry-film thickness is
40 μm or greater.
NOTE If the nominal thickness is less than the surface roughness
of the substrate, the uncertainty of the measurement will
increase.