Why is performing a pre-clean important in liquid penetrant testing?

Performing a pre-clean in liquid penetrant testing is essential to ensure the surface is free of contaminants. The presence of dirt, grease, oil, rust, paint, or other surface coatings can prevent the penetrant from adequately seeping into the surface flaws, which may lead to false results or missed indications. Cleaning the surface helps to ensure that any potential discontinuities—such as cracks or porosity—are uncovered and can be accurately identified by the penetrant. This step is critical because it directly affects the reliability and effectiveness of the testing process, ensuring that the results are valid and that any defects present are correctly highlighted for evaluation.