Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Metal or metal alloy
Reexamination Certificate
1999-08-02
2001-05-29
Bell, Bruce F. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Metal or metal alloy
C205S730000, C205S740000, C204S196150, C204S196160, C204S196190, C204S196200, C204S196330, C204S196370, C427S105000, C427S424000, C427S425000, C427S427000, C264S008000, C264S013000, C264S540000, C264S542000, C264S563000, C264S173170, C264S177140, C264S209100, C264S212000, C264S228000, C264S249000, C264S309000, C264S310000, C156S429000
Reexamination Certificate
active
06238545
ABSTRACT:
DISCLOSURE
This invention relates to cathodic protection of metal structures such as pipelines, a composite anode-electrolyte pipe section, and methods of making such pipe sections, as well as forming the pipeline, and applying cathodic protection to the pipeline.
BACKGROUND OF THE INVENTION
Cathodic protection is defined as either (1) the reduction of corrosion rate by shifting the corrosion potential of the electrode toward a less oxidizing potential by applying an external electromotive force or (2) the partial or complete protection of a metal from corrosion by making it a cathode, using either a galvanic or impressed current. Cathodic protection is well established method by which a metal can be protected from corrosion. It is used anywhere the structure and anode are embedded in a common electrolyte, such as, on pipelines, tanks, piers, pilings, bridge decks and substructures.
Cathodic protection is accomplished by causing a flow of direct current (DC) between another electrode (called the anode) and the structure (called the cathode). The DC causes the surface of the structure to become polarized, thus stopping or reducing corrosion.
In an impressed current cathodic protection system, a rectifier normally converts AC to DC and supplies the current; and the anode is a relatively inert material that can transfer the current to the soil or water, which is the normal electrolyte. In a galvanic system, the anode is an electrochemically active metal compared to the cathode, and the current is a natural occurrence of connecting the anode and cathode together.
The chemical reaction at the anode is metal oxidation, with oxygen, or chlorine evolution. Both ions and electrons are formed at the anode. Ions generated by the reaction flow to the cathode via the electrolyte. The electrons flow to the cathode via a connection. Reduction occurs at the cathode, which consumes the electrons. Three common cathodic reactions in cathodic protection are as follows:
O
2
+2H
2
O+4e→4OH
−
O
2
+4H
+
+4e→2H
2
O
2H
+
+2e→H
2
In all cases, both electron and ionic currents are involved in cathodic protection. That is, both a continuous common electrolyte and a metallic connection between the anode and cathode are required. The metallic connection is provided through the rectifier. The soil, water, or other conductive medium provides the common electrolyte.
In cathodic protection practice, anodes may be installed in the ground or water where the anodic reactions take place. Anodes can be installed in several different configurations depending on the requirements; these include (1) a single point using shallow anodes, (2) evenly spaced along the structure (distribution system), or (3) in a deep well. Common anode materials include pure metals, alloyed metals, platinum coated valve metals, valve metals having electrochemically active coatings, and certain ceramic materials.
If a separation or void in the electrolyte occurs between the anode and cathode, the current will stop, and cathodic protection will fail. Conditions where the electrolyte becomes discontinuous between anode and cathode can and do occur in practice. Examples of situations where this could occur include: coarse backfill materials that are too coarse to permit intimate or uniform contact with the structure surface (e.g., gravel, rocks); where fine backfill is washed away from the environment surrounding the structure from groundwater flow leaving voids against the structure containing only air; and in exposed situations where fine backfill is not possible or practical to place.
The application of anode material embedded in concrete for the cathodic protection of steel reinforcement in concrete bridge decks and substructures, piers, and buildings is common. The use of an anode embedded in an acidresistant cement liner containing an anode for the cathodic protection of stainless steel flue gas ducts is disclosed in U.S. Pat. No. 5,290,407. This patent applies to the protection of stainless steel flue gas ducts that are exposed to an environment consisting of a thin-film acidic condensate in an otherwise atmospheric environment. There is a significant problem in providing proper cathodic protection with respect to buried steel structures such as pipelines, where the natural environment consists of rocks or other materials that present voids or prevent full contact between the structure and environment.
SUMMARY OF THE INVENTION
The principal aspect of the invention is the use of an anode material embedded in a conductive layer that has been applied to the surface of a metallic structure such that the anode and conductive layer and structure form a composite, and from which a self-contained cathodic protection system can be constructed. The invention is pre-applied to the structure, and the anode, electrolyte, and structure are installed as a composite. The use of a concrete coating on the structure or pipe also serves as an anti-buoyancy mass to keep the structure or pipe from floating, and further serves as a protective casing.
The cathodic protection system of the present has the following advantages:
1. A continuous backfill surrounding the structure is not necessary since the conductive layer, anode, structure, and power supply (if used) form a self-contained cathodic protection system; therefore, cathodic protection can be applied to structures in environments where a continuous surrounding electrolyte is difficult, expensive, or impossible to achieve.
2. The anode provides a continuous distributed current source that provides an even current distribution to the structure.
3. A separate anode bed is not necessary since the anode and electrolyte are integrated with the structure.
4. Cathodic protection is then possible in areas where the right-of-way is too narrow to use conventional anodes, such as the single point, distribution systems, or deep well systems noted above.
It is also an aspect of the invention to provide a process for constructing a cathodic protection system with the structure itself, as well as a process for forming a composite section of the structure which includes the structure section, the anode and the electrolyte.
REFERENCES:
patent: D. 206605 (1967-01-01), Versoy et al.
patent: D. 219218 (1970-11-01), Eisele
patent: D. 223665 (1972-05-01), Eisele
patent: D. 223666 (1972-05-01), Eisele
patent: 2491225 (1949-12-01), Stearns
patent: 2594000 (1952-04-01), Elliott
patent: 2602980 (1952-07-01), Bryan
patent: 3260661 (1966-07-01), Kemp et al.
patent: 3343081 (1967-09-01), Lane
patent: 3349017 (1967-10-01), Ziegler
patent: 3354063 (1967-11-01), Shutt
patent: 3581922 (1971-06-01), Versoy et al.
patent: 3614605 (1971-10-01), Eisele
patent: 3661624 (1972-05-01), Versoy et al.
patent: 3674546 (1972-07-01), Harris et al.
patent: 3700223 (1972-10-01), Elliott
patent: 3718309 (1973-02-01), Harris
patent: 3743470 (1973-07-01), Bickham
patent: 3747192 (1973-07-01), Harris et al.
patent: 3777705 (1973-12-01), Harris et al.
patent: 3784349 (1974-01-01), Bickham
patent: 3807588 (1974-04-01), Bickham
patent: 3894637 (1975-07-01), Bickham
patent: 3924562 (1975-12-01), Harris et al.
patent: 3937382 (1976-02-01), Cunningham et al.
patent: 3985848 (1976-10-01), Frische et al.
patent: 4004619 (1977-01-01), Eddlemon et al.
patent: 4006049 (1977-02-01), Gardner
patent: 4051436 (1977-09-01), Weir, Jr.
patent: 4058428 (1977-11-01), Case et al.
patent: 4073760 (1978-02-01), Harris et al.
patent: 4091291 (1978-05-01), Foster et al.
patent: 4096017 (1978-06-01), Wyke et al.
patent: 4126718 (1978-11-01), Christie et al.
patent: 4141130 (1979-02-01), Hart et al.
patent: 4160329 (1979-07-01), Scrimshaw
patent: 4205544 (1980-06-01), Foster
patent: 4205774 (1980-06-01), Madden et al.
patent: 4213357 (1980-07-01), Lively et al.
patent: 4244740 (1981-01-01), Harris
patent: 4249477 (1981-02-01), Christie et al.
patent: 4267029 (1981-05-01), Massarsky
patent: 4284385 (1981-08-01), Lively et al.
patent: 4333783 (1982-06-01), Gardner
patent: 4366972 (1983-01-01), Franklin
patent: 4506485 (1985-03
Allebach Carl I.
Smith Albert A.
Young Walter T.
Bell Bruce F.
Renner , Otto, Boisselle & Sklar, LLP
LandOfFree
Composite anode, electrolyte pipe section, and method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Composite anode, electrolyte pipe section, and method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Composite anode, electrolyte pipe section, and method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2502026