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ASNT Level III- Visual & Optical Testing

My Level III Self Study Notes Reading 4 Section 4B

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7.4 Using Etchants<br />

After proper surface preparation and safe mixing of<br />

etchants, the application of etchants to the test object may be<br />

done with immersion or swabbing. The technique is determined<br />

by the characteristics of the etchant being used.<br />

7.4.1 immersion<br />

During immersion, a test object is completely covered by<br />

an etchant contained in a safe and suitable material- glass can be used for<br />

most etchants except hydrofluoric acid, fluorine<br />

materials, strong alkali and strong phosphoric acid.<br />

A glass heat resistant dish on a hot plate may be used for<br />

heated solutions. The solution should be brought to temperature<br />

before the test object is immersed. Tongs or other handling<br />

tools are used and the test object is positioned so that<br />

the test surface is face up or vertical to allow gas to escape.<br />

The solution is gently agitated to keep fresh etchant in contact<br />

with the test object.<br />

Charlie Chong/ Fion Zhang

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