Pesky Penetrant Contaminants
Although the major components of penetrant inspection products usually cause no problems with the metals with which they contact when
used correctly, there are some minor contaminants that can cause problems and which must be limited in certain applications. The governing specification, SAE AMS 2644E, has taken a broad view of this by requiring that the penetrant materials be non corrosive. This requires that the penetrant materials pass corrosion tests in order to be listed on the Qualified Products List (QPL): ¶3.3.1. These tests are as follows:
- ¶22.214.171.124 Moderate temperature corrosion of steel, aluminum, and magnesium.
- ¶126.96.36.199 High temperature stress corrosion of titanium.
- ¶188.8.131.52 High temperature corrosion of cast nickel alloys
While these tests satisfy most customers’ requirements, there are situations that demand additional tests for specific element content.
ASME Boiler and Pressure Vessel Code Vol. V, Article 6, T-641, Appendix II requires that the sulfur and halogen content be limited.
¶ II-641 states that penetrants used on Nickel Based Alloys must contain less than 1 % (10000 ppm) of Sulfur. ¶II-642 states that penetrants used on Austenitic Stainless Steel & Titanium must contain less than 1% (10000 ppm) total Halogens (chlorine & fluorine).
Pratt & Whitney’s FPM requires that analyses be made for Sulfur, Sodium, Fluoride and Chloride. The limits of these in penetrants is S <
0.1% (1000 ppm), Na < 0.01% (100 ppm), F < 0.005% (50 ppm), & Cl < 0.04% (400 ppm).
ISO/FDIS-3452 control for Sulfur is less than 0.02% (200 ppm) and total Halogens less than 0.02% (200 ppm).
Elemental requirements keep getting tighter and tighter but the inspection materials have a 1000 times less of these elements than the
inspectors finger prints. Where are the dirty hand controls?