Can someone explain to me in lamans term what all is involved.  I had to do a Hastelloy structural test and the inspector said this was how my coupons were going to be tested.

from ESAB website..."This method of testing typically involves the removal of small samples of the welded joint.  These samples are polished across their cross-section and then etched using some type of mild acid mixture, dependent on the base material used.

The acid etch provides a clear visual appearance of the internal structure of the weld.  Particular interest is often shown at the fusion line, this being the transition between the weld and the base material.  Such items as depth of penetration, lack of fusion, inadequate root penetration, internal porosity, cracking and inclusions can be detected during inspection of the etched sample.

   This type of inspection is obviously a snapshot of the overall weld length quality when used for sampling inspection of production welds.  This type of testing is often used extremely successfully to pinpoint welding problems such as crack initiation, when used for failure analyses."