US3314874A - Apparatus for determining cathodic protection - Google Patents

Description

April 1967 R. w. FLOURNOY APPARATUS FOR DETERMINING CATHODIC PROTECTION Filed March 21, 1963 INVENTOR. ROWLAND w. FLOURNOY BY 2 4 I z His ATTORNEYS United States Patent APPARATUS FOR DETERMINING CATHODIC PROTECTION Rowland W. Flournoy, Henrico County,

Reynolds Metals Company, tion of Delaware Filed Mar. 21, 1963, Ser. No. 267,042 2 Claims. (Cl. 204-195) This invention relates to an improved method and apparatus for determining whether proper cathodic protection will be provided for a particular metal member, such as an aluminum pipe line or the like, when utilized with a particular sacrificial anode and a particular electroly-te. This invention also relates to an improved method for making such an apparatus or the like.

It is well known that when a metallic pipe line is to be laid in soil, submerged in a body of water, or utilized to convey a particular liquid, the pipe line in combination with other dissimilar metal members of the pipe line system forms a battery-like structure wherein the electrolyte is the environmental liquid of the pipe line system, such as the wet soil, the body of water, or the liquid being conveyed through the pipe line.

Such a natural battery causes excessive pitting and corrosion of the metal of the pipe line system unless a very active and sacrificial anode is provided for the system to render the metal members of the pipe line system substantially cathodic so that the sacrificial anode will be eaten away rather than the metal members of the pipe line system because of the environmental battery arrangement previously described.

However, it has been found that no satisfactory means has heretofore been provided for readily and simply testing whether a particular pipe line when utilized with a particular sacrificial anode and the particular environmental electrolyte will result in proper cathodic protection for the pipe line.

According to the teaching of this invention, however, an improved apparatus is provided for simply testing, either in the field or in the laboratory, whether proper cathodic protection will be provided for a particular metal member, such as a pipe line or the like, when utilized with a particular sacrificial anode and a particular electrolyte. Such apparatus is so constructed and arranged that the same can be utilized by inexperienced personnel as the same does not require manipulation of switches, potentiometers, galvanometers, or other complicated electrical devices. Further, the apparatus of this invention is readily portable, rugged in design and substantially unitary.

Accordingly, it is an object of this invention to provide an improved method for determining whether proper cathodic protection will be provided for a particular metal member when utilized with a particular sacrificial anode and a particular electrolyte, the method of this invention having one or more of the novel features set forth above or hereinafter shown or described.

Another object of this invention is to provide an improved apparatus for determining whether proper cathodic protection will be provided for a particular metal member when utilized with a particular sacrificial anode and a particular electrolyte, the apparatus having one or more of the novel features set forth above or hereinafter shown or described.

A further object of this invention is to provide an improved method for making such an apparatus or the like.

Other objects, uses and advantages of this invention are apparent from a reading of this description which proceeds with reference to the accompanying drawings forming a part thereof and wherein:

FIGURE 1 is a perspective view illustrating one embodiment of the improved apparatus of this invention.

Va., assignor to Richmond, Va., 21 corpora- 3,314,874 Patented Apr. 18, 1967 FIGURE 2 is a cross-sectional view taken on line 22 of FIGURE 1.

FIGURE 3 is a schematic view illustrating the electrical circuitry of the apparatus of FIGURE 1.

FIGURE 4 is a view similar to FIGURE 3 and illustrates another embodiment of this invention.

While the various features of this invention are hereinafter described and illustrated as being particularly adaptwhether proper cathodic protection will be provided for other metal members as desired.

Therefore, this invention is not to be limited to only the embodiments illustrated in the drawings, because the drawings are merely utilized to illustrate one of the wide variety of uses of this invention.

Referring now to FIGURES 1 and 2, an improved apparatus of this invention is generally indicated by the reference numeral 10 and is adapted to readily indicate whether proper cathodic protection will be provided for a particular pipe line structure when utilized with a particular sacrificial anode and a particular environmental electrolyte.

For example, should it be desired to determine whether a particular pipe line, formed of aluminum-containing a particular sacrificial anode of a particular metal or alloy thereof and with a particular environmental electrolyte, such as the moisture in the soil that is to receive the pipe line structure, the body of water in which the pipe line is to be submerged, or the particular liquid to be conveyed through the pipe line system, the apparatus 10 can be formed in the following manner.

A sample of the metal of the pipe line system is provided and the same is indicated by the reference numeral 11 in FIGURES 1 and 2. a

For example, the sample 11 can comprise a section of the cylindrical pipe which is to form the desired pipe line system whereby the sample 11 comprises a cylindrical sleeve having opposed ends 12 and 13 and is approximately 6 inches more or less in length.

A sample of the particular sacrificial anode to be utilized with the particular pipe line structure is formed in the manner illustrated in FIGURE 2 and is generally indicated by the reference numeral 14, the metal anode comprising a length of metal folded against itself in the manner illustrated in FIGURE 2.

For example, the sample pipe line 11 can comprise aluminium alloy 6063, 6 061 or 3003 while the sample anode 14 can comprise aluminum, zinc, magnesium or alloys thereof.

The above-mentioned aluminum alloys 6063, 6061 and 3033 have the following composition: The aluminum alloy 6063 comprises 0.20.6% silicon, 0.35% iron, 0.10% copper, 0.10% manganese, OAS-0.9% magnesium, 0.10% chromium, 0.10% zinc, 0.10% titanium, 0.05% other metals with the remainder being aluminum; the aluminum alloy 6061 comprises 04-08% silicon, 0.7% iron, 0.15-O.40% copper, 0.15% manganese, 0.8- 1.2% magnesium, 0.l50.35% chromium, 0.25% zinc, 0.15% titanium, 0.5% other metals with the remainder being aluminum; and the aluminum alloy 3003 comprises 0.6% silicon, 0.7% iron, 0.20% copper, l.0-1.5% manganese, 0.81.3% magnesium, 0.10% zinc, 0.05% other metals with the remainder being aluminum.

The sample of the pipe line 11 and the sample of the sacr' cial anode 14 are interconnected together by an insulating member 15 in such a manner that the anode 14 :is concentrically disposed in the sleeve 11 and electrically insulated from the sleeve 11 by the member 15.

In particular, the member 15 may have a plate-like section 16 adapted to rest on the end 12 of the sleeve 11 and have an inset portion 17 adapted to be telescopically received in the end 12 of the sleeve 11 whereby the insulating member 15 is adapted to: be secured to the sleeve 11 by threaded fastening members 18 passing through the sleeve 11 and into the reduced portion 17 of the member 15. The anode 14 can pass centrally through the insulating member 15 in the manner illustrated in FIGURE 2 and can be secured thereto in any suitable manner.

Therefore, it can be seen that the apparatus interconnects together the samples 11 and 14 in such a manner that the same are adapted to be simultaneously immersed in a body of the particular electrolyte involved. For example, such electrolyte can be contained in a container 19 in the manner illustrated in FIGURE 3 or such electrolyte can be in its environmental stage whereby the apparatus 10 is taken to the site location and manually immersed the desired depth in the naturally occurring electrolyte.

An ammeter 20 is carried by insulating member of the apparatus 10 and is secured to the cross member 21 of a U-shaped bracket 22 having its legs 23 secured to the insulating member by threaded fastening mem bers 24 in the manner illustrated in FIGURE 2.

A relatively small dry cell battery 25 or the like \is disposed adjacent the insulating member 15 and rests on the end 12 of the sleeve 11, the battery 25 being mounted to the insulating member 15 by suitable wire leads in a manner hereinafter described.

A suitable transistor 26 :is disposed on the insulating member 15 and is secured thereto by proper electrical leads in a manner hereinafter described.

Therefore, it can be seen that the apparatus 10 provides a substantially unitary structure formed from a relatively small number of basic parts electrically interconnected together in a manner now to be described.

As illustrated in FIGURE 3, the transistor 26 has a base terminal 27, an emitter terminal 28 and a collector terminal 29 in the conventional manner, the transistor 26 either being of the PNP type or the NPN type as desired. However, the particular transistor utilized with the embodiment of the apparatus 10 illustrated in the drawings is of the PNP type.

The sacrificial anode sample 14 of the apparatus 10 is electrically interconnected to the 'base terminal 27 of the transistor 26 by electrical lead 30.

The pipe line sample 11 is electrically interconnected to the emitter terminal 28 of the transistor 26 by a lead 31.

The positive terminal 32 of the battery 25 is also electrically interconnected to the emitter terminal 28 of the transistor 26 by a lead 33 joined to the previously described lead 31.

The negative terminal 34 of the battery 25 is electrically interconnected to the collector terminal 29 of the transistor 26 by a lead 35, the lead 35 being disposed on opposite sides of the ammeter whereby the ammeter 20 is disposed in the lead 35 to measure the amperage of the current flow passing therethrough in a manner later to be described.

After the apparatus 10 has the end 13 thereof submerged in the particular electrolyte 36 as illustrated in FIGURE 3, the electrolyte 36 either being in the field or contained :in the laboratory, a potential subsequently exists between the anode 14 and the pipe line sample 11 whereby a small current flows through the circuit provided by the leads 30 and 31 and the transistor 26 in a manner well known in the art.

If the particular electrolyte 36 being utilized is of a certain form, the current flows from the anode 14 to the pipe line sample 11 whereby the anode sample 14 forms an anode of the battery and the pipe line sample 11 forms a cathode thereof.

Because the samples 11 and 14 are relatively small the same are immersed in the electrolyte 36 for only a depth of approximately four inches whereby the resultant current produced in the circuit provided by the leads 30 and 31 and transistor 26 is relatively small. Accordingly, it is desired to amplify the current by means of the transistor 26 and the battery 25.

For example, as the circuit flows through the transistor 26 from the battery effect of the samples 11 and 14 and electrolyte 36 in the manner previously described, the transistor 26 causes an amplified and proportional flow of circuit to flow from the negative terminal 34 of the battery 32 through the lead 35, transistor 26 and the lead 33 to the positive terminal 32 of the battery 25.

The ammeter 20 not only indicates the magnitude of the amperage of the above described amplified current flow, but also the ammeter 20 indicates whether the amplified current flow is in the proper direction to provide proper cathodic protection for the pipe line sample 11. For example, should the meter reading be negative, it can be seen that the current flow between samples 11 and 14 is in the wrong direction for cathodic protection while a positive reading on the ammeter 20 indicates that the current flow between the samples 11 and 14 is in the proper direction for cathodic protection of the pipe line sample 11.

The ammeter 20 must be rugged and have a sensitivity of l milliampere for full scale deflection. Other meters with higher or lower sensitivity may be employed as required. However, to utilize the one milliampere ammeter 20, the transistorized simple amplifier circuit previously described is employed for the following reasons.

The transistor 26 permits the use of a less expensive ammeter 20 for readings of protective current.

Further, the transistor 26 reduces the electrical current flowing between the anode 14 and cathode sample 11 to normal values avoiding polarization, possible current reversal and other undesirable effects.

The transistor 26 amplifies the current readings to come on the range of the meter scale with an amplification factor of approximately 10 to l to provide readings equivalent to the protective current in milliamperes per square foot of cathode surface.

It has been found that protective current readings will be positive and show deflection on the meter scale in the range of 20% to of the dial reading in order to indicate normal cathodic protection achievement.

Therefore, it can be seen that the apparatus 10 is a substantially unitary structure which can provide a reading on the dial of the ammeter 20 by merely placing the lower end 13 of the sample 11 into the electrolyte supply 36 to a depth of approximately four inches. However, depth readings are not critical since high current flows are not required between the anode 14 and cathode 11.

Thus, the apparatus 10 can be utilized by inexperienced personnel because the same does not require manipulation of switches, potentiometers, galvanometers or other complicated electrical devices.

Further, the small pen cell or battery 25 can be of approximately one and one-half volts and is soldered into the circuit whereby the same will normally have a life of several years which is equivalent to the shelf-storage life for the battery 25.

Thus, failure of the unit to read can be interpreted as a dead battery, loose connection on transistor, meter deficiency, or other condition requiring repair of the unit. No interpretation of results or change of the equipment is required.

Since four simple components are required to construct the apparatus 10, such as the section of cathode material which may be a section of the pipe line, a section of the anode material, which may be aluminum, zinc, magnesium, a combination of alloys or other materials, a simple transistor requiring less than one dollar for replacement, and a one and one-half volt miniature dry cell or the like, it can be seen that the apparatus is relatively inexpensive when formed according to the teachings of this invention.

It can further be seen that the cathodic protection evaluation ammeter 20 predicts whether protective current flow is in the right direction by positive reading clockwise on the dial and whether the protective cur-rent flow in milliamperes per square foot is in the normal range of approximately one to five milliamperes per square foot.

Due to the amplification factor of the ammeter 20, a small anode l4 and cathode 11 can be employed to predict current flows in specific units such as milliamperes per square foot.

While the amplification generally can be accomplished in one stage, as illustrated in FIGURE 3, it is to be understood that several stages of amplification can be used, if required, while the apparatus will still maintain the compact character previously described.

While the apparatus found that the same is tection between aluminum alloys and other materials, including other alloys of aluminum.

While the circuitry for the apparatus 10 illustrated in FIGURE 3 is useful with electrolytes that produce relatively 10w voltages, it may be desired to provide an apparatus 10 which can be utilized with electrolytes which produce even higher voltages. For example, brackish waters and the like might produce 3 milliamperes per square foot and the voltage produced by such waters may be between one volt and 1% volts.

Under these conditions, the circuitry for the apparatus 10 can be modified in the manner illustrated in FIGURE 4 wherein parts similar to the described are indicated by like lowed by the reference lete-r a.

For example, the apparatus 10a illustrated in FIG- URE 4 is substantially the same as the apparatus 10 illustrated in FIGURE 3, except certain resistances have been imposed in the circuit.

circuit in the In the same manner, resistances 39 and 40 can be respectively disposed on opposite sides of the battery 25a in order to hold down the flow of current in the amplifier circuit and waters or electrolytes that they expect to use with a rep resentative cathode sample 11a and anode sample 14a.

waters in any particular locality that has that particular type of electrolyte water.

For example, a three miliampere ammeter 20a would That type of ammeter 20a has less resistance than the one milli- 40 are introduced to hold down the current which would otherwise be increased by the small resistance of the three milliampere ammeter 20a.

Therefore, it can be seen that various modifications can be made of the apparatus of this invention while still performing the same functions taught by this invention.

While the form of the invention now preferred has been disclosed as required by the statutes, other forms may be used, all coming within the scope of the claims which follows.

What is claimed is:

1. A self-contained and portable apparatus for determining whether proper cathodic to provide an amplified current flow in the proper range for proper cathodic protection of said pipe line whereby no adjustments or computations are required by the user, said pipe line sample being a cylindrical sleeve, said anode being mounted inside said sleeve. 2. An apparatus asset forth in claim 1 wherein said insulating member is secured to one end of said sleeve.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES National Bureau of Standards, Journal of Research, volume 10, 1948, pages 301, 313. HOWARD S. WILLIAMS, Primary Examiner. JOHN H. MACK, Examiner. T. H. TUNG, Assistant Examiner.

Claims (1)

1. A SELF-CONTAINED AND PORTABLE APPARATUS FOR DETERMINING WHETHER PROPER CATHODIC PROTECTION WILL BE PROVIDED FOR PARTICULAR PIPE LINES WHEN UTILIZED WITH A PARTICULAR SACRIFICIAL ANODE AND A PARTICULAR ENVIRONMENTAL ELECTROLYTE COMPRISING A SAMPLE OF SAID PIPE LINE, A SAMPLE OF SAID ANODE, AN INSULATING MEMBER INTERCONNECTING SAID SAMPLES TOGETHER SO THAT SAID SAMPLES CAN BE SIMULTANEOUSLY IMERSED IN SAID ELECTROLYTE, A CONDUCTOR MEANS CONNECTING SAID SAMPLES TOGETHER AND BEING ADAPTED TO HAVE A CURRENT FLOW THERETHROUGH WHEN SAID SAMPLE ARE IMMERSED IN SAID ELECTROLYTE, AND CIRCUIT MEANS CONNECTED TO SAID CONDUCTOR MEANS, SAID CIRCUIT MEANS BEING ADAPTED TO PROVIDE AND AMPLIFIED CURRENT FLOW PROPORTIONAL TO SAID

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