Method and apparatus for measuring accumulated and instant rate of material loss or material gain

Abstract

Apparatus for measuring accumulated and instant rate of material loss or material gain of metal elements for the detection of metal deposition and corrosion includes a metal probe that is inserted into a measurement environment, causing the probe to experience metal deposition or corrosion. The probe has a corrosion-resistant first section and a corrodible second section. A temperature-compensated circuit receives an input signal from each of the first and second sections of the probe, whereby the circuit maintains a substantially constant voltage across the first section and generates a reference signal and a measurement signal. The circuit conditions and converts the reference signal and the measurement signal to produce first and second digitized output signals for inputting to a microprocessor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a Continuation-in-Part of co-pending application Ser. No. 10 / 166,571; filed Jun. 10, 2002, which, in turn, is a Continuation of International Application No. PCT / DK00 / 000689; filed Dec. 11, 2000. The disclosures of both of the aforementioned applications are incorporated herein by reference.FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT [0002] Not Applicable BACKGROUND OF THE INVENTION [0003] This invention relates to a method and an apparatus for measuring accumulated and instant rate of material loss or material gain of metal elements for the detection of metal deposition (material gain) caused for example during deposition of coatings used in plating processes and corrosion (material loss) caused for example in pipelines during transportation of hazardous media. [0004] The state of the art provides several techniques for quantification of accumulated corrosion and instant corrosion rate as for example disclosed in Br...

AI Technical Summary

Benefits of technology

[0009] A particular advantage of the present invention is the provision of a temperature independent measurement of accumulated and instant rate of material loss or material gain accomplished without use of a temperature sensor device.

[0010] A further advantage of the present invention is the provision of measurement and balancing of real and imaginary voltage components variations endured by a measuring probe.

[0011] A particular feature of the present invention is the provision of compatibility of the present invention to numerous probes having different physical attributes and having different physical dimensions.

[0019] (g) a first sensor amplifier having a first sensor amplifier input connected to said first connector of said coated section of said metal element, having a second sensor amplifier input connected to said second connector of said non-coated section of said metal element, and having a first sensor output generating a first sensor amplifier output signal constituted by an amplification of said first metal element voltage, said second metal element voltage and / or a voltage difference between said second metal element voltage and said first metal element voltage,

[0020] According to the basic realisation of the first aspect of the present invention the voltage difference between the coated and non-coated section of the metal element or probe provides a measurement of accumulated corrosion, whereas the second resistance in conjunction with time related changes of the second resistance at one temperature provides a measurement of instant rate of material loss or material gain. The resistance of the metal element constituted by the first resistance and said second resistance of may be in a range from 4 μΩ to 4 KΩ such as ranges 4 mΩ to 400 mΩ or 10 mΩ to 100 mΩ.

[0021] The apparatus according to the first aspect of the invention provides the possibility to apply a wide variety of probes or metal elements for measuring accumulated or instant rate of material loss or material gain. This compatibility further ensures that the apparatus generates repeatable measurements irrespective of probe type.

Problems solved by technology

However, since these techniques require a conducting electrolyte system e.g. a stable water phase they are not applicable in a corrosion process when water is not continuously present.

Further, even though the requirements for performing electrochemical measurements are present inaccurate results may occur induced by additional current responses from redox-processes other than those involved in the particular corrosion process, which additional current responses may superimpose on the current response from the corrosion process and cause inaccurate or misleading results.

In addition, the interpretation of the results of a measurement performed using one of the generally applied electrochemical techniques often requires a specific expertise and knowledge of the user.

None of the techniques provides a fast measurement of instant rate of corrosion or in other words the resolution of these techniques is insufficient.

However, the resistance of the test coupon and the resistance of the reference coupon are highly temperature dependent.

Consequently, the effect of temperature variations from one measurement to another will cause unwanted inaccuracies in the measurements and decreases the comparability of the individual measurements included in a series of measurements.

However this kind of temperature compensation obviously introduces further inaccuracies in the measurement since the temperature characteristics of the temperature sensor device are not identical to the temperature characteristics of the test coupon or the reference coupon.

Images