Other

Southwest Research Institute

Corr Instruments, Llc.

Lietai Yang Yang

Xiaodong Sun Yang

Kuang-Tsan Kenneth Chiang

Narasi Sridhar

As the development of DC transit systems continues, many of the buried pipelines and metal structures close to the metro system have experienced accelerated corrosion by the dynamic DC stray current. Because of the dynamic feature of the stray currents, monitoring the effect of the dynamic stray current on the corrosion of the buried structures has been a challenging task. This invention discloses a method to use a multielectrode system to measure the effect of dynamic stray currents on the corrosion of a metal structure or buried pipeline. The method also measures the effectiveness of cathodic protection under the influence of stray current. High-voltage power transmission lines that produce a changing magnetic field, which in turn produces an alternating current flowing through the berried pipe or other structures that run in parallel with the transmission lines. The method disclosed in this invention may also be used to detect the effect of the interference of the alternating current.

Multielectrode probes for monitoring fluctuating stray current effects and AC interference on corrosion of buried pipelines and metal structures

A method for preventing the formation of gas bubbles inside a high pressure reference electrode in the electrolyte-filled section, and thus eliminating the gas bobble effect on the electrical continuity, was disclosed. One or more thin solid rods or tubes are inserted into the internal electrolyte-housing tube and the thin rods or tubes alter the surface tension of the gas bubbles so that the bubbles are unstable in the middle of the liquid electrolyte. Compared with the fiber wicks or porous powder used by previous researchers to ensure the electrical continuity, the thin tubes or rods are easy to handle and easy to clean. This method may also be used in other systems that contain a liquid-filled vertical or sloped tube (e.g., a pH electrode) to prevent the formation of gas bubbles in the liquid-filled section of the tube.

High pressure reference electrode and a method to eliminate the formation of gas bubbles in vertical or sloped liquid-filled tubes

Electrochemical probes for corrosion monitoring in an environment that may cause the formation of electron conducting deposits and the method for making such probes were disclosed. The probes have exposed fingered electrodes. Except for the sensing areas at the tip sections, all surfaces of the exposed electrodes are coated with an inner electrically insulating coating or tubing and one or more additional coating(s) or tube(s). One of the additional coatings is ion conducting. The electrodes are spaced such that there are gaps between the outer surfaces of the neighboring electrodes to prevent the formation of a continuously distributed electron conducting deposits between the sensing surface of one electrode and the sensing surfaces of the other electrodes. These probes are especially suitable for applications in gas systems and oil-water mixtures containing hydrogen sulphide (HS).

Electrochemical probe with coated, fingered electrodes for corrosion monitoring in oil-water mixtures and gas systems containing hydrogen sulfide

Systems and methods for real time detection of corrosion of rebars embedded in a concrete structure. Test bars are selected for corrosion testing purposes, and may or may not also be part of the concrete reinforcement structure. These test bars are coated, and exposed sections of these test bars form a network of node electrodes. Electrical measurement from a counter electrode near a node electrode provides an indication of corrosion at that node electrode. Using a system of node electrodes and counter electrodes, a large concrete area may be monitored, and if corrosion is indicated, a methodical selection of electrodes can be used to locate the corrosion. The same concepts may be applied to detect corrosion in buried structures, such as pipelines and tanks.

Corrosion monitoring of concrete reinforcement bars (or other buried corrodable structures) using distributed node electrodes

A long-term, reliable high pressure reference electrode for high temperature applications was disclosed. This reference electrode has inner and an outer liquid junction plugs. The inner plug provides the function of restraining the outflow of the internal reference electrolyte. The outer plug is chemically and mechanically robust in the external fluid where the reference electrode is used and protects the inner plug from the mechanical and chemical attacks by the harsh external fluid. Therefore, the inner plug can be selected from many of the well-characterized liquid junction plugs used in regular low temperature reference electrodes, without the need for the inner plug to be chemically and mechanically stable in the external fluid, as long as it has the thermal stability. A method for preventing the formation of gas bubbles inside a high pressure reference electrode in the electrolyte-filled section, and thus eliminating the gas bobble effect on the electrical continuity, was also disclosed. One or more thin solid rods or tubes are inserted into the internal electrolyte-housing tube and the thin rods or tubes alter the surface tension of the gas bubbles so that the bubbles are unstable in the middle of the liquid electrolyte. Compared with the fiber wicks or porous powder used by previous researchers to ensure the electrical continuity, the thin tubes or rods are easier to handle and easier to clean. This method may also be used in other systems that contain a liquid-filled tube (e.g., a pH electrode) to prevent the formation of gas bubbles in the liquid-filled section of the tube.

High temperature and high pressure reference electrode and method to eliminate the formation of gas bubbles in liquid-filled tubes

Electrochemical probes for corrosion monitoring in an environment that may cause the formation of electron-conducting deposits and the method for making such probes were described. The probes have long exposed electrodes. Except for the tip section, all surfaces of the exposed electrodes are coated with a coating or covered with electrically insulating tubing, so that only the tip section has uncovered metal that serves as the active areas of the electrodes. The coating or tubing material is such that the deposits cannot easily form on its surfaces. Because the electrical bridging between the active areas of any two electrodes requires the deposition of an evenly distributed layer of the electron-conducting deposits along the path from one area to the other area, the coated surface reduces the possibility of short-circuiting for the active areas of the electrodes. These probes are especially suitable for applications in systems containing hydrogen sulphide (HS).

Electrochemical probes for corrosion monitoring in hydrogen sulfide systems and methods of avoiding the effect of electron-conducting deposits

A method based on the measurement of the oxidation power or the cathodic current density using a corrosion-resistant electrode (noble electrode) to derive the bounding corrosion rates of the corroding metal, which is either a stand-alone electrode or an actual component of an equipment, is disclosed. During the measurement, the potential of the noble electrode is controlled at the corrosion potential of the corroding metal. A modified version the sensor that provides a correction factor for the estimation of the corrosion rate according to the bounding corrosion rate is also disclosed. The correction factor is derived based on the cathodic currents measured for the noble electrode and for the corroding metal at a potential that is significantly lower than the corrosion potential, so that the measured cathodic current density from the corroding metal equals the true cathodic current density on the corroding metal.

Oxidizing power sensor for corrosion monitoring

Disclosed herein is an electrochemical corrosion sensor. The sensor may include an array of electrodes wherein each electrode may include a diamond like carbon coating disposed on at least a portion of the electrodes. The coating thickness may be at least about 1 micron. The electrodes may therefore provide relatively more accurate determination of electrode corrosion rates that may be more consistent with coupon type gravimetric testing.

Apparatus for measuring electrochemical corrosion

Methods of deriving the cumulative maximum localized corrosion rate and cumulative localized corrosion rate factor for corrosion monitoring using coupled multielectrode array sensor probes are disclosed. Compared with maximum localized corrosion rate, which is derived from the corrosion rate on any of the electrodes of a probe that has the highest corrosion rate at a given moment of time, cumulative maximum localized corrosion rate is derived from the corrosion rate of the electrode that has been corroded the most in a given time period. The cumulative maximum localized corrosion rate is directly related to the corrosion damage (maximum localized corrosion depth); the maximum localized corrosion depth equals the integration of the cumulative maximum localized corrosion rate. Cumulative maximum localized corrosion rate should be used to evaluate the localized corrosion effect on metal damage.

Measurement of cumulative localized corrosion rate using coupled multielectrode array sensors

The bounding corrosion rate is measured with a coupled multielectrode array sensor by decoupling a select number of anodic electrodes on the sensor from the coupling joint. In doing so, all or most of the electrons produced on the anodic electrode that remains connected to the coupling joint are forced to flow to the coupling joint and are thus measured. Because of the large number of electrodes on a multielectrode array sensor, one of them may become contaminated by foreign materials during the measurements or polishing process. The effect of such an electrode on the performance of the sensor can be eliminated by automatically disconnecting it from the coupling joint.

Methods for measuring bounding corrosion rates using coupled multielectrode sensors and eliminating the effects of bad electrodes

Methods of using multihole and multiwire sensors to measure general and localized corrosion penetration rates near real time are disclosed. The multihole penetration sensor is included of multiple electrodes embedded in individual cavities that are formed by a metal whose external surface is exposed to a corrosion environment. The distance between the inner surface and the external surface of the cavities (wall thickness) varies from one cavity to the other. The electrical resistance or current between each of the electrodes and a common electrode exposed to the same corrosion environment changes significantly when the wall of the cavity in which the electrode resides is perforated by corrosion and the corrosion medium is in contact with the electrode. The corrosion penetration rate is calculated by dividing the wall thickness of the different cavities by the time it takes to penetrate these cavities.

Multihole and multiwire sensors for localized and general corrosion monitoring

A method of measuring localized corrosion, using a multi-electrode array sensor. The method eliminates the effect of internal current in corroded electrodes, and thus provides a more accurate corrosion measurement. In one embodiment, the potential of a common node of the sensor is adjusted so that the sensor's most cathodic current is close to zero.

Method for measuring localized corrosion rate with a multi-electrode array sensor

A sensor array for measuring localized corrosion based on electrochemical reactions is disclosed. The sensor has an array of electrodes that are made from the material of interest. The electrodes are electrically insulated from each other and arranged so that a small area of the electrode contacts a corrosive environment. The voltage outputs across the electrodes connected to the electrodes are measured and used as the signals to indicate localized corrosion.

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Minden, NV, United States of America

Lietai Yang Yang