Accession Number : ADA293344

Title :   Evaluation of Electrochemical Noise to Monitor Corrosion for Double Hull Applications.

Corporate Author : NAVAL SURFACE WARFARE CENTER CARDEROCK DIV BETHESDA MD

Personal Author(s) : Murray, John N.

PDF Url : ADA293344

Report Date : AUG 1994

Pagination or Media Count : 49

Abstract : The use of electrochemical noise (EC noise) as a non-destructive evaluation (NDE) method for characterizing the status of organic barrier coated steel surfaces was evaluated in the laboratory for possible application to Navy double-hull applications. External hull and internal tankage/space conditions were simulated by evaluating previously aged samples outside and inside a Faraday cage. The voltage noise E(sub n) signal was shown to be considerably larger when measured outside the cage and the same general result of higher noise signals from "better" coatings was observed for both conditions. Measurements of the sample noise outside the cage include both coating/substrate interfacial electrochemical noise and local stray electrical effects as the high impedance coating systems act as an antenna. Although the particular commercial E(sub n) data gathering program was found to collect less of the total E(sub n) signal for samples outside the cage because of a limitation in intermediate data storage, the signal was sufficient for laboratory evaluations. The usefulness of evaluations of hull surfaces while in industrial drydock conditions remains to be established. Latex and epoxy coated electrochemical sensors were also evaluated for applicability in non-immersion situations such as the interior double-hull spaces. Although the EC Noise data were limited, electrochemical impedance spectroscopy data showed the sensors to respond in 75 and 100% relative humidity (RH) atmospheres but only to a limited degree in 29% RH. jg

Descriptors :   *CORROSION, *ELECTROCHEMISTRY, *NOISE, *SHIP HULLS, TEST AND EVALUATION, SIMULATION, DETECTORS, NONDESTRUCTIVE TESTING, SPECTROSCOPY, NAVY, VOLTAGE, SUBSTRATES, ELECTRICAL PROPERTIES, STEEL, SURFACES, COATINGS, SIGNALS, ORGANIC MATERIALS, DATA STORAGE SYSTEMS, SPACE(ROOM), EPOXY COMPOUNDS, STORAGE TANKS, IMPEDANCE, DRYDOCKS, LATEX.

Subject Categories : Physical Chemistry
      Inorganic Chemistry
      Properties of Metals and Alloys
      Marine Engineering
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE