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
|Publication Date:||1 September 2012|
|ICS Code (Paint coating processes):||87.020|
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
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.