Liquid Penetrant Testing Level 2 (PT-2) Practice Exam

What additional surface preparation should be performed on a soft aluminium test piece after sand blasting?

1. Etching

2. Solvent cleaning

3. Ultrasonic cleaning

4. Grinding

The correct answer is: Ultrasonic cleaning

In the context of preparing a soft aluminium test piece for liquid penetrant testing, after sand blasting, ultrasonic cleaning is the most effective method for ensuring that the surface is adequately prepared. Sand blasting may leave behind residues or particles that can interfere with the penetrant’s ability to enter any surface discontinuities, and ultrasonic cleaning provides a thorough cleaning process that can eliminate these contaminants. Ultrasonic cleaning employs high-frequency sound waves in a cleaning solution, creating cavitation bubbles that effectively dislodge contaminants from the surface, including those that may be embedded in microscopic crevices or pores. This technique is particularly advantageous for soft aluminium, as it minimizes the risk of further damaging the surface compared to more aggressive methods. By achieving a pristine surface condition without affecting the integrity of the soft aluminium, ultrasonic cleaning enables the penetrant to perform optimally during the inspection process. Other methods such as etching, solvent cleaning, and grinding could potentially alter the surface characteristics of the aluminium piece or fail to remove residual contaminants as thoroughly, making them less suited for ensuring optimal conditions for liquid penetrant testing.