Gas Turbine Testing - Corrosion Coating Evaluation

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VEXTEC Laboratory Group's small gas turbine testing rig provides an excellent way to evaluate corrosion coatings. In a program with the Air Force, we produced approximately the same field service corrosion damage that accumulated in 5,000 hours of usage, with 300 hours of testing. The photos below show field service & rig damage.

Corrosion Damage from actual usage
Actual Field Damage
Corrosion Damage from test rig
Test Rig Produced Damage


Since the corrosion was due to sulfidation, sulfur was added to the exhaust stream. Agricultural grade sulfur was mixed with water to obtain a concentration of 1730 parts per million. The mixture was constantly stirred to keep it uniform as it was pumped into the exhaust stream at a rate of 6.8 gallons per hour. Since the desired temperature was 300F, it was necessary to bring room temperature air into the exhaust stream, which was done by adapting a leaf blower. The blades were rotated at a speed of 5500 RPM. The purpose of the program was to evaluate 3 different coatings. 10 blades were tested: The following mission profile was repeatedly applied to the blades:
Mission Profile for Corrosion Testing
Mission Profile for Corrosion Testing

After 200 hours of testing, all specimens were examined carefully. Their conditions are shown below in photographs.
Mission Profile for Corrosion Testing
Coating A After 200 Hours of Testing
Mission Profile for Corrosion Testing
Coating B After 200 Hours of Testing
Mission Profile for Corrosion Testing
Coating C After 200 Hours of Testing


After evaluating the specimens, it was decided there was no point in testing coating A further. The test was continued for another 100 hours with coatings B & C. Those coatings were evaluated again after a total of 300 hours.
Mission Profile for Corrosion Testing
Coating B After 300 Hours of Testing
Mission Profile for Corrosion Testing
Coating C After 300 Hours of Testing

Summary

VEXTEC Laboratory Group VEXTEC Laboratoy Group
1033 South Hunt Street
Terre Haute, IN 47803
VEXTEC - America's Most Promising Company
America's Most Promising Company
Forbes Magazine - October, 2009
E-mail
epope@vextec.com
URL
http://gas-turbine-testing.com/corrosion-coating-evaulation.htm
Phone
1-317-750-3414
Ed Pope
Copyright © 2012 VEXTEC