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ASNT Level III- Visual & Optical Testing

My Level III Self Study Notes Reading 4 Section 4B

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7.3 Etching<br />

7.3.1 Choice of Etchant<br />

The etchant, its strength, the material and the discontinuity<br />

all combine to determine surface finish requirements (see<br />

Table 15). Properly selected etchants chemically attack the<br />

test material and reveal welds (Fig. 70), pitting (Fig 71),<br />

grain boundaries, segregation, laps, seams, cracks aria heat<br />

affected zones. The indications are highlighted or contrasted<br />

with the surrounding base material.<br />

Charlie Chong/ Fion Zhang

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