Electrolysis: processes – compositions used therein – and methods – Electrolytic analysis or testing – For corrosion
Reexamination Certificate
1999-04-15
2001-07-10
Tung, T. (Department: 1743)
Electrolysis: processes, compositions used therein, and methods
Electrolytic analysis or testing
For corrosion
C204S400000, C204S404000, C204S280000, C205S775500
Reexamination Certificate
active
06258253
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of electrochemistry. More specifically, the present invention relates to a real-time, quantitative electrochemical device for the measurement of corrosion of conductive materials in atmospheres containing chemically reactive gases and water vapor.
2. Description of the Related Art
Many metal-containing devices and structures must function in corrosive atmospheres which cause them to deteriorate over time. Corrosion may take the form of metal oxides resulting from reaction with oxygen in the air, or corrosion may form by compounds formed with the effluent of industrial processes, such as hydrogen sulfide.
A common method of measuring corrosion employs resistance measurement of a metallic corrodible test element to indicate, by change in electrical resistance, the amount of metal that has been lost by corrosion over a period of time. There are several corrosive probes, sensors or processes currently available for evaluating corrosive environments by measuring an electric current passed through the corrosive media itself.
U.S. Pat. No. 4,752,360 to Jasinski discloses a corrosion probe having sandwich of electrodes and dielectric layers for measuring the corrosion rates of metals in corrosive environment. In one application, the probe must be immersed in a liquid corrosive media, including corrosive elements such as carbon dioxide or hydrogen sulfide in a brine solution used in oil drilling. Current is conducted through the conductive elements and directly through the liquid brine. U.S. Pat. No. 4,049,525 to Dutton is related to a corrosion test cell having a plurality of conductive elements connectable to test electrodes, wherein the electrodes extend into a corrosive liquid environment during operation. The corrosion measuring cell of Schiessl, U.S. Pat. No. 5,015,355, includes a plurality of electrodes which are embedded in a solid (concrete) media for sensing the occurrence of corrosion of steel bars by sensing variations in current flow between the electrodes. The sensed current is again a current flowing through the corrosive media.
The prior art is deficient in the lack of a real-time, quantitative electrochemical device for measuring corrosive potential in a gaseous environment. The present invention fulfills this long-standing need and desire in the art.
SUMMARY OF THE INVENTION
The present invention is directed to a real-time, quantitative electrochemical device for the measurement of corrosion of conductive materials in a gaseous environment containing chemically reactive gases and water vapor. This device is called a vapor corrosion cell herein. This vapor corrosion cell contains strips of alternating dissimilar conducting materials, usually metals or alloys, such as Ti and Al strips, separated by a thin strip of non-conducting material in a sandwich structure. All the strips of each similar conducting material are electrically connected. The edges of the strips are exposed to the atmosphere containing water vapor and a reactive vapor or gas. Under these conditions, an electrochemical potential is developed between dissimilar metals and if the electrical circuit is closed, a current flows. Measurement of the current indicates electrochemical activity and thus the corrosion occurring at the exposed surfaces.
In one embodiment of the present invention, there is provided an apparatus for measuring corrosion in an environment, the apparatus comprising a series of strips of a first conducting material (M
1
) alternated by a series of strips of a second conducting material (M
2
), separated by a thin strip of non-conducting material in a sandwich structure. All of the strips of each similar conducting material are electrically connected. The cell, having the dimension as small as 50 mm×50 mm×10 mm (length×width×depth), is further connected to a current measuring/recording device, such as an ammeter. The resulting apparatus provides a real-time and quantitative measurement of corrosion. Preferably, the non-conducting separating strip is selected to be as thin as 0.025 mm. More preferably, from about 4 to about 10 strips of M
1
and an equal number of strips of M
2
are used.
In one embodiment, the environment contains chemically reactive gases and/or water vapor. Examples of reactive gases are carbon dioxide, nitrogen dioxide, sulfur dioxide, hydrogen halides, ammonia, hydrogen sulfide and other nitrogen-containing acids.
In another embodiment, the conducting materials are usually metals or alloys, such as aluminum, zinc, titanium, copper, etc. M
1
can be an active sacrificial material, while M
2
can be a test or reference material.
In another embodiment of the present invention, there is provided an apparatus for measuring corrosion in an environment, comprising interleaved combs of dissimilar conducting materials deposited on a non-conducting surface, such as a glass surface.
In yet another embodiment of the present invention, there is provided a method of measuring corrosion in an environment by exposing the apparatus to the environment and measuring the current and potential characteristics of the apparatus, wherein the measurement indicates electrochemical activity and thus the corrosion occurring.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention given for the purpose of disclosure.
REFERENCES:
patent: 3954590 (1976-05-01), Czuha
patent: 4049525 (1977-09-01), Dutton et al.
patent: 4587479 (1986-05-01), Rhoades et al.
patent: 4752360 (1988-06-01), Jasinski
patent: 4994159 (1991-02-01), Agarwala et al.
patent: 5015355 (1991-05-01), Schiessl
patent: 5188715 (1993-02-01), Chen et al.
patent: 5208162 (1993-05-01), Osborne et al.
patent: 5290407 (1994-03-01), Syrett et al.
patent: 5310470 (1994-05-01), Agarwala et al.
patent: 5411890 (1995-05-01), Falat
patent: 5481198 (1996-01-01), Patel
patent: 5529668 (1996-06-01), Hall
patent: 5531103 (1996-07-01), Eaton
patent: 5639959 (1997-06-01), Reiber
patent: 5712559 (1998-01-01), Moore et al.
Cate James M.
The United States of America as represented by the Administrator
Tung T.
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