What test procedure could lead to false signals if the specimen is inadequately cleaned?

Penetrant testing is a non-destructive testing method used to detect surface-breaking defects in non-porous materials. This testing method relies on the ability of a liquid penetrant to seep into cracks or flaws on the surface of the specimen. If the specimen is not adequately cleaned prior to applying the penetrant, residues like dirt, grease, or old paint can obstruct the penetrant's ability to enter the defects. As a result, this could lead to false signals, indicating that no defects are present when, in fact, they might exist beneath the contaminants.

In contrast, hardness testing, tensile testing, and ultrasonic testing do not have the same vulnerability to false signals caused by surface contamination. Hardness testing often requires only a small area of the material to be assessed, and while surface preparation can influence the results, it does not generally lead to false Readings in the same way that penetrant testing can. Tensile testing assesses the material's strength by pulling a specimen until it breaks; although surface condition can impact the outcome, it typically does not generate false signals regarding the presence of defects. Ultrasonic testing, which uses sound waves to detect internal flaws, is also less affected by surface cleanliness than penetrant testing, as sound waves can penetrate