Corrosion related activities at ARL address both corrosion testing and research. With an emphasis on identifying, analyzing, and understanding corrosion issues, as well as defining and testing appropriate solutions. Research thrusts focus on optimizing corrosion resistant coating performance, corrosion resistant alloy comparisons, and the mechanisms of crevice corrosion. Analytical techniques including optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) are utilized to examine corroded specimens.
General Corrosion Testing
Corrosion testing at ARL covers a wide range of techniques including electrochemical testing (DC: potentiodynamic and cyclic polarization, AC: electrochemical impedance spectroscopy (EIS)), immersion testing, material compatibility (galvanic corrosion), and salt spray (pitting and crevice corrosion). Laboratory resources consist of potentiostats, high-impedance voltmeters, solution analytical equipment, alternate immersion chamber, and a Singleton Cyclic Corrosion Test Chamber. Standardized tests frequently employed are ASTM B117 Salt Spray, G71 Galvanic Corrosion, G44 Alternate Immersion, G85 Modified Salt Spray, G60 Cyclic Humidity, G5 Polarization Measurements, G150 Critical Pitting Temperature, GM9540P, and SAE J2334. |
Electrochemical Corrosion Test Cell |
ASTM G44-94 Alternate Immersion Testing |
Singleton Cyclic Corrosion Test Chamber |
Hot Corrosion Testing
PSU/ARL is unique in that it is one of the few facilities having Type 1 (900°C) and Type II (705°C) hot corrosion testing capabilities with controlled SO2 environments through the use of the Dean Rig apparatus. The Dean rig test apparatus will be used to evaluate various materials under Type I (900°C) and Type II hot corrosion (705°C). The apparatus generally consists of a multi-temperature zone furnace, alumina tube, molten sodium sulfate salt, and an O2-0.1%SO2 gas mixture. At one end of the furnace, the O2-0.1%SO2 carrier gas mixture is passed through a platinized honeycomb catalyst upstream from the crucible containing the sodium sulfate (contained in an alumina crucible) maintained at approximately 900°C (temperature above the sodium sulfate melting temperature of 884°C). The salt sprayed test specimens are then positioned in an alumina crucible (705°C) downstream from the molten sodium sulfate. The difference in temperature along the various zones of the furnace allows the vaporized sodium sulfate salt to condense onto the surface of the test specimens held at the lower temperature 705°C (Type II hot corrosion). Sodium sulfate salt is added to an alumina boat at the start of the experiment in order to maintain the equilibrium amount of SO3 which stabilizes the activity of the sodium sulfate allowing an accelerated corrosion method of the test specimens. The salt sprayed specimens are then placed in an alumina tray contained in the lower temperature zone (705°C) of the Dean Rig for evaluation under Type II hot corrosion conditions.
Schematic illustration of Deans Rig testing apparatus (left) and temperature profile within two of the heat zones (right).