Test Report
Study of 6NHClCorrosiononCommercial 316SS, HastelloyC-22 andTrueTubeVariants
Notes on theResultingTestData
Commercial 316LSS is used as the base for all relative corrosion resistance rankings.
HastelloyC-22 is included in the test because it is recognized as the ‘material of choice’ for HCl service. Test
results illustrate a 44 fold improvement in corrosion resistance to6NHCl over the base commercial 316LSS.
The corrosion rate of the commercial grade fused silica coated tube varied between samples, more than all other
tubes tested. The average corrosion rate for commercial grade fused silicawas 4.75mpyor a 6 fold improvement
over commercial 316LSS.
Test results clearly illustrate that TrueTubeEP improves the corrosion resistance byapproximately2 fold over
commercial 316LSS.
UsingTrueTubeEP as the substrate of theSiltek coating improved the corrosion resistance by27 fold over
commercial grade fused silica coated tubing and 172 fold over commercial 316LSS in themilled condition. The
resultingTrueTubeEPS showed far less variance then the commercial grade fused silica coated tubing. The
average corrosion ratewas calculated tobe 0.28mpy. This gives TrueTubeEPS a 104 fold advantage over
commercial 316LSSmaterial with a veryhigh confidence level.
Conclusion
The corrosion resistance of austenitic stainless steel can be improved byelectropolishing or byapplying a coating
of fused silica or bycombining both processes. The combination ofO’BrienCorporation electropolishedTrueTube
EP and theSiltek coating byRestek provided corrosion resistance superior to that ofHaselloyC-22.
Surface preparationwill affect the abilityof any subsequent process toprovide additional corrosion protection. This
assertion is supported by the variance found in the testing of the fused silica coating on commercial grade tubing.
The corrosion rate of these samples varied sixteen timesmore than all other sample sets. The samples of fused
silica applied to commercial tubing showed corrosion resistance changes from a lowof 3 fold to a high of 24 fold.
While the average corrosion rate for commercial grade fused silica computed to4.75mpyor a 6 fold improvement
over commercial grade tubing, ranking by the average value belies the uncertaintyof predicable performance.
While verydifferent in their values both TrueTubeEP andTrueTubeEPS provided constant results and enhanced
corrosion protection.
©2004O’BrienCorporation •QLT-TRTTCORR • 11AUG04
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