When measuring the Dry Film Thickness Of liquid coatings applied to galvanized ferrous substrates the most commonly used instrument is the:

NACE No.13/ SSPC 6 identifies the use of:

Measuring methyl ethyl ketone (MEK) resistance of ethyl silicate inorganic zinc-rich primers by solvent rub requires

You are NACE Level 2 Inspector working on a tank lining job where a mobile centrifugal blast unit is being used to blast the tank floor to a NACE No.1/SSPC SP 5. The Contractor has completed his final blast and has called for a hold point inspection. This is the 1 st time you have seen field based centrifugal blast cleaning. You observe what appears to be staining on the substrate however the Contractor assures you this is normal when using centrifugal blast units and what you are seeing is what is defined in the standard as an acceptable variation in appearance.
Your FIRST preferred course of action is to:

External coatings applied to buried pipelines are generally tested for: