Which material is not suitable for liquid penetrant testing?

Which material is not suitable for liquid penetrant testing?

• A. A porous plastic material
• B. A nonporous metal
• C. A ceramic material
• D. A rubber composite

Answer: (A)

Liquid penetrant testing works best on nonporous surfaces because the penetrant must stay on the surface to enter defects and then be drawn out for a clear indication. A porous plastic material has open pores that absorb the penetrant into the material itself. The penetrant soaks into these pores rather than just revealing surface-breaking flaws, causing background staining and masking real indications. That makes flaw detection unreliable. So, porous plastic is not suitable for this method. Nonporous metals and most ceramics provide clean, surface-only access for the penetrant, allowing clear, interpretable indications. A rubber composite can vary, but the porosity issue in the plastic example is the key reason it’s unsuitable.

Liquid penetrant testing works best on nonporous surfaces because the penetrant must stay on the surface to enter defects and then be drawn out for a clear indication. A porous plastic material has open pores that absorb the penetrant into the material itself. The penetrant soaks into these pores rather than just revealing surface-breaking flaws, causing background staining and masking real indications. That makes flaw detection unreliable. So, porous plastic is not suitable for this method.

Nonporous metals and most ceramics provide clean, surface-only access for the penetrant, allowing clear, interpretable indications. A rubber composite can vary, but the porosity issue in the plastic example is the key reason it’s unsuitable.