Inspection Instruments and Tests Flashcards

An inspector is required to measure the dry film thickness (DFT) of a coating system on a large, flat steel surface totaling 500 square meters (approx. 5,000 sq ft). According to SSPC-PA 2, how should the inspector determine the number of areas to measure?

Answer: Measure three 10 m² areas for the first 100 m², and then one additional 10 m² area for each subsequent 100 m².

SSPC-PA 2 specifies a clear procedure for determining the number of measurements on large surfaces. For areas over 100 m² (approx. 1,000 ft²), the standard requires the inspector to measure three 10 m² (approx. 100 ft²) areas for the first 100 m², and then arbitrarily select and measure one additional 10 m² area for each additional 100 m² or increment thereof.

Which of the following instruments is used to perform a quantitative pull-off adhesion test as described in ASTM D4541?

Answer: A portable adhesion tester with a loading fixture (dolly)

ASTM D4541, 'Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers', describes a quantitative method for measuring adhesion. This test involves affixing a loading fixture, often called a dolly, to the coating surface with an adhesive and then using a portable adhesion tester to apply a perpendicular force to pull the dolly off, measuring the force required for detachment.

A coating inspector is preparing to conduct holiday testing on a new protective coating with a specified dry film thickness of 15 mils (381 microns) on a conductive substrate. Which type of holiday detector is most appropriate for this application?

Answer: A low-voltage, wet-sponge holiday detector

NACE SP0188 provides guidance on holiday testing. For coatings less than 20 mils (500 microns) thick on conductive substrates, a low-voltage (typically 67.5V or 90V) wet-sponge holiday detector is the recommended instrument. High-voltage detectors are used for thicker coatings and can damage thinner films if the voltage is not set correctly or is too high.

An inspector uses replica tape and a micrometer to measure the surface profile of an abrasive blast-cleaned steel surface, following the procedure in NACE SP0287. What is the primary purpose of this test?

Answer: To measure the peak-to-valley depth of the surface anchor pattern

NACE SP0287, 'Field Measurement of Surface Profile of Abrasive Blast-Cleaned Steel Surfaces Using a Replica Tape', describes a method to quantify the surface roughness or anchor profile. The replica tape captures a reverse image of the surface profile, and a micrometer is then used to measure the thickness of the impression, which corresponds to the peak-to-valley height.

During a coating application project, the specification requires adhesion testing according to ASTM D3359, Method A. This test is primarily intended for which of the following scenarios?

Answer: Field testing of coating systems greater than 5 mils (125 µm) in thickness

ASTM D3359 describes two methods for tape adhesion testing. Method A, the X-cut test, is primarily intended for use at job sites and for coating systems with a total thickness greater than 5 mils (125 µm). Method B, the cross-hatch test, is more suitable for thinner coatings, typically under 5 mils.

Which of the following methods would be used to retrieve a sample for assessing the concentration of soluble salts on a steel surface prior to coating?

Answer: Using a Bresle patch or adhesive patch to extract surface contaminants

SSPC-Guide 15 and ISO 8502-6 describe methods for retrieving soluble salts from a surface for analysis. The Bresle patch method involves attaching an adhesive patch with a reservoir to the surface, injecting a specified amount of deionized water, massaging the water to dissolve the salts, and then extracting the solution for conductivity measurement.