ASNT Level III- Visual & Optical Testing
My Level III Self Study Notes Reading 4 Section 4B
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