Liquid Penetrant Testing Level 1 (PT-1) Practice Exam

What is the danger of sandblasting without subsequent chemical etching for cleaning surfaces to be penetrant tested?

1. The surface may become too smooth

2. The discontinuities may be peened over and closed

3. The test may require more time

4. Increased material loss

The correct answer is: The discontinuities may be peened over and closed

The danger of sandblasting without subsequent chemical etching lies in the potential for discontinuities to be peened over and closed. When surfaces are sandblasted, they are subjected to high-velocity impacts from abrasive materials, which can result in the formation of a thin layer of compressed material on the surface. This peening effect can cause surface cracks, voids, or other discontinuities to be flattened or sealed, making them inaccessible to penetrants during testing. Chemical etching serves to remove this hardened layer and any debris left from the blasting process, thereby exposing these discontinuities. If the surface remains unetched, any flaws present may not be detected during the penetrant testing process, which defeats the primary purpose of the inspection. This can lead to significant safety risks, as undetected flaws may compromise the integrity of the component being tested. While the other options might relate to aspects of surface preparation for testing, they do not address the critical issue of undetected flaws due to the effects of peening, which is paramount in ensuring effective liquid penetrant testing.