What is the primary hazard of using sandblasting for cleaning surfaces prior to penetrant testing?

The primary hazard of using sandblasting for cleaning surfaces prior to penetrant testing is that it may close discontinuities. During the sandblasting process, the abrasive material can force particles into small cracks or other surface defects, effectively sealing them. This can prevent penetrants from entering these discontinuities during the inspection process, leading to false conclusions about the integrity of the material. If these hidden flaws are not detected, it may result in undiagnosed structural weaknesses that could lead to failure in critical applications.

In contrast, while a smooth finish might hide defects, it is the risk of closing the defects that poses a more significant challenge during penetrant testing. The removal of surface contaminants is generally a goal in preparing surfaces for testing, and although leaving sand particles could introduce errors, it is the sealing of discontinuities that most directly interferes with the effectiveness of the penetrant inspection.