Comparison of rating techniques for JFTOT heater tube deposits

The Visual Rating method and the ALCOR Mark 8A Tube Deposit Rater, used to rate deposits that form on the Jet Fuel Thermal Oxidation Tester (JFTOT) heater tubes, were compared to each other and to measurements of the deposit thickness. An Auger Electron Spectrometer, used in conjunction with an ion gun (AES/Ion Gun), was used to measure the deposit thickness and composition. Both the Visual Rating method and the Mark 8A Tube Deposit Rater were found to correlate with deposit thickness measurements to a limited degree. The AES/Ion Gun method proved to be a useful laboratory tool for measuring the relative thickness of deposits and the elemental composition of deposits (except for hydrogen and helium). Deposits that have a spectrum of colors (i.e., peacock or rainbow type deposits) were found to be considerably thicker than Code 3 deposits. Thin film light interference was found to be the cause of the peacock associated with these deposits.