Electrolysis: processes – compositions used therein – and methods – Electrolytic analysis or testing – For corrosion
Reexamination Certificate
1998-11-30
2001-07-24
Tung, T. (Department: 1743)
Electrolysis: processes, compositions used therein, and methods
Electrolytic analysis or testing
For corrosion
C204S404000, C205S777000
Reexamination Certificate
active
06264824
ABSTRACT:
The present invention relates to the assessment of corrosion.
Electrochemical noise measurements have been used as a means of monitoring corrosion for a number of years, a utilising potential and current measurements. Conventional techniques generally rely on a visual examination of the raw time record data, requiring expertise in the interpretation of the nature of the signals and the calculated values as described.
According to a first aspect of the present invention, there is provided a method for identification of corrosion of a metal object, comprising the steps of providing electrode means capable of generating electrochemical noise signals, and analyzing the statistical distribution of the signals to provide an indication of parameters of the corrosion, said parameters being selected from the group consisting of the extent and the nature of the corrosion.
Preferably at least two electrodes are provided and are exposed to the same corrosion conditions as the metal object, and at least one of the electrodes (preferably two) are fabricated from the same material as the metal object. The signals analyzed from the electrode means can be current or voltage noise, and it is preferred to measure the current between two electrodes and optionally to measure the potential between one of said two electrodes and at least one other electrode.
Typically, analyzing the statistical distribution of the measured values includes the steps of removing the mean value of the measurements, followed by normalisation of the measurements. Typically, the measurements are normalised to one standard deviation. This allows for direct comparison of data sets comprising the measured values from different sources.
Typically, analyzing the statistical distribution of the measured values further comprises the stop of calculating the kurtosis and/or skewness of the measured values. The kurtosis and/or skewness values can be used to indicate the type of corrosion.
Where the potential or current measurements drift significantly, analyzing the statistical distribution typically includes a further step of trend removal.
Typically, a neural network may be used to facilitate interpretation of the statistical distribution. Alternatively, an expert systems approach or alternative pattern recognition techniques may be used. This allows for the data to be analyzed without the requirement for personnel who are experts in the visual interpretation of the data.
According to a second aspect of the present invention, there is provided apparatus for assessing corrosion of a metal object, comprising electrode means capable of generating electrochemical noise signals, and means for calculating the statistical distribution of the signals to indicate parameters selected from the group consisting of the extent and the nature of the corrosion.
Preferably the electrodes are exposed to the same corrosion conditions as the metal object, and at least two of the electrodes are fabricated from the same material as the metal object. Current measuring means is preferably electrically connected between the said two electrodes and potential measuring means is optionally electrically connected between one of said two electrodes and at least one other electrode.
Typically, the processing means for calculating the statistical distribution includes a computer. Typically, the processing means reads the measured values of current and/or potential and processes these to provide the statistical distribution. In preferred embodiments the skewness and kurtosis is assessed. The processing means may store the measured values of current and potential and may also output them to a recording means. The recording means may be a plotter, printer or the like. Alternatively, the measured values may be stored in a memory device, such as on hard disk.
The output of the processing means is typically a statistical distribution of the measured values. The output may be displayed on a monitor and/or stored in the memory device. The output may also be recorded on the recording means.
Typically, the processing means includes an expert system or an alternative pattern recognition system. Such systems may be a neural network, for example, and are used to analyze the output of the processing means to determine the corrosion mechanism.
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Leslie W. Flott, “Nonnormal Frequency Distributions”, Metal Finishing, May 1995, pp. 52-57.
Eden David Anthony
Reid Stephen Anthony
Integriti Investments Ltd.
Ratner & Prestia
Tung T.
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