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Investigations of environmental degradation of materials by measurement of electrolyte parameters using microsensors and microelectrodes

Fink, Klaus Michael
http://rave.ohiolink.edu/etdc/view?acc_num=case1058210033

Abstract Details

1995, Doctor of Philosophy, Case Western Reserve University, Materials Science and Engineering.
A series of corrosion sensors were developed, tested and used for three important industrial applications: buried gas and oil pipelines, heat exchangers in gas fired appliances and automotive air conditioning evaporators. These sensors were able to measure the time-of-wetness, pH, temperature, and Cl ion concentration, in situ, in restricted areas, and in real time. This data could then be used in predictive models, to make materials selection decisions, and to evaluate alternate designs rapidly for improved corrosion performance. Two time-of-wetness sensors were developed and inserted into different structures. Interdigitated fingers (IDF) type probes are amenable to insertion on flat surfaces, while concentric ring type sensors are useful for insertion into crevices, radiators and similar structures. Work with the IDF probe showed usefulness as a RH sensor as well as a conductivity sensor in restricted access areas. The use of iridium and its derivatives as a pH sensor showed film growth variations, dependence of calibration on growth processes, and electrode stability in various electrolytes. The study also revealed previously unknown problems with immersion in solutions con taining thiosulfate and bisulfite. Experiments were conducted with a novel reference electrode, based on Ag/Ag×Sy films, with potential stability in a wide range of solutions and temperatures and promising results were obtained. Resistance track temperature sensors, designed and tested, are consistent with future strategies of multi-element corrosion transducers. Heat exchangers in gas fired residential heating appliances showed corrosion problems as efficiency of furnaces have increased. Sensor measurements during the operation of these appliances showed that the initial and final condensates formed in the heat exchangers had a pH of less than 2. Additions of Freon-12 to the precombustion gas stream increases corrosion rates and decreased the local pH within the condensates. Protecting pipeline steel beneath previously disbonded coating systems is important to reduce potential failures due to corrosion. Measurements beneath disbonded tape coatings on pipelines showed that cathodic protection induces chemical changes beneath disbonded tape which can protect pipeline steel, even when cathodic currents are not able to access the steel beneath the disbonded tape sections. Hydroxyl ions generated at the exposed steel surface were observed to transport down the length of the crevice and create a deaerated, alkaline environment within the crevice. These measurements also showed that the alkalinity, transported into the crevice, can be washed out if the potential source is disconnected. Automotive air conditioning evaporators routine collect condensates during operation. These regions remain wet and cause corrosion problems. Application of corrosion sensors to these evaporators, made from aluminum alloys, showed that previously assumed wetness times were incorrect and suggested solutions would not address the corrosion and aesthetic issues. (Abstract shortened by UMI.
Joe Payer (Advisor)
186 p.
environmental degradation; measurement; electrolyte parameters; microsensors; microelectrodes

Recommended Citations

Citations

  • Fink, K. M. (1995). Investigations of environmental degradation of materials by measurement of electrolyte parameters using microsensors and microelectrodes [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1058210033

    APA Style (7th edition)

  • Fink, Klaus. Investigations of environmental degradation of materials by measurement of electrolyte parameters using microsensors and microelectrodes. 1995. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1058210033.

    MLA Style (8th edition)

  • Fink, Klaus. "Investigations of environmental degradation of materials by measurement of electrolyte parameters using microsensors and microelectrodes." Doctoral dissertation, Case Western Reserve University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058210033

    Chicago Manual of Style (17th edition)

case1058210033
658
© 1995, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.