US2918420A

US2918420A - Electrolytic system

Info

Publication number: US2918420A
Application number: US602156A
Authority: US
Inventors: Rolland C Sabins
Original assignee: Sabins Dohrmann Inc
Current assignee: Sabins Dohrmann Inc
Priority date: 1956-08-06
Filing date: 1956-08-06
Publication date: 1959-12-22
Anticipated expiration: 1976-12-22
Also published as: NL109089C; DE1156626B; DE1154331B; NL219618A

Description

Dec. 22, 1959 R. c. SABINS 2,918,420

ELECTROLYTIC SYSTEM Filed Aug. 6, 1956 3 Sheets-Sheet 1 g N 1 I I a i 8 I I 1 l I a I N m L 2 I o m w I0 I 3 JNVENTOR. ROLLAND a. sAam/s BY I M4 [#5547 ATTORNEYS Dec. 22, 1959 R. c. SABINS ELECTROLYTIC SYSTEM 5 Sheets-Sheet 2 Filed Aug. 6, 1956 INVENTOR. HOLLAND G. SABINS BY I -M ATTORNEYS Dec.22, 1959 RQSABINS 2,918,420

ELECTROLYTIC SYSTEM Filed Aug. 6, 1956 3 Sheets-Sheet 3 66 HOV.A.C.

FIG. 3

IN VEN TOR. ROLL A ND 0. SA Bl/VS zhzmw mzzfi 7 ATTORNEYS United States Patent ELECTROLYTIC SYSTEM Rolland C. Sabins, San Diego, Calif., assignor, by direct and mesne assignments, to Sabins Dohrmann, Inc., San Francisco, Calif., a corporation. of California Application August 6, 1956, Serial No. 602,156

4 Claims. (Cl. 204-196) The present invention relates to an electrolytic system which among many other uses has particular utility in preventing corrosion, or what is understood as preventing galvanic dissolution by cathodic protection, and is a continuation-in-part of my copending application Serial No. 586,969, filed May 24, 1956, for Corrosion Prevention System.

My improved system includes an electrolyte, a cathode and an anode-cathode immersed in the electrolyte, the anode-cathode functioning as an anode with respect to said cathode, and, in one aspect of the invention, 1 employ a third element which functions as an anode in its relationship with the anode-cathode.

In carryingout my invention, 1 impress electric current on the cathode, and, in the aspect of the invention in which one of the metals functions as an anode as well as a cathode, I also impress electric current on it. I also utilize a reference half-cell; it is also submerged in the electrolyte and is utilized as a reference element in a circuit for determining the potential of the cathode and the anode-cathode. For example, in the circuit including a steel cathode, sea water electrolyte, the half-cell and an exterior conductor between the half-cell and steel, the steel has a potential of 630 millivolts, when no extraneous electric current is impressed on the circuit, and in a cirthat, to protect a ships steel hull from corrosion, a potential must exist of approximately 890 millivolts, and accordingly the potential of the steel cathode (herein the ships hull) must be raised 260 rnillivolts to prevent what is known as galvanic corrosion or dissolution of the steel. Similarly, magnesium can be protected from passing into solution if its potential is raised from 1590 to 2105 millivolts, namely, raised 515 millivolts.

It has been found, however, that when the reference half-cell is subjected to various environments, its resist ance to the flow of current is increased, i.e., it becomes negatively polarized. Obviously, if the resistance to current flow of the half-cell varies, it cannot function constantly as a reference. I have discovered that the reference half-cell can be rejuvenated, i.e., its abnormal resistance to flow of current removed by depolarizing the same. This is accomplished by subjecting the half-cell to the positive side of a source of direct current.

In certain embodiments or aspects of the invention, I provide a field instrument including a millivolt meter, a dry cell battery, and suitable switch mechanism. In one embodiment, the switching mechanism is such that when the mechanism is properly electrically connected to the steel of the ships hull and half-cell, the potential of the hull is readable on the millivoltmeter, and then by 2,918,420 Patented Dec. 22, 1959 ice actuating a simple switch, the positive side of the dry cell is connected with the half-cell to rejuvenate the same.

In another embodiment of the field instrument, the switch mechanism is provided with a third position, i.e., an ofF position in addition to the potential measure position and the half-cell rejuvenating position.

Still in another embodiment, the switch mechanism ineludes four positions; in addition to the hull potential measure position, the half-cell rejuvenating position, the stop position, it includes a position in which the potential of the magnesium can be measured.

Another important feature of the present invention lies in the automatic control of rejuvenating the reference halfcell and the varying of the impressed current on cathode. When the current value falls in the reference circuit, due for example to polarization of the reference half-cell or due to an increase in potential of the cathode (herein the steel hull), then a cycle of automatic control is instituted including the immediate impressing of direct current to the half-cell to rejuvenate, i.e., depolarize the same, and simultaneously decrease the current impressed on the cathode. This phase of the cycle of rejuvenating the half-cell and the decreasing of current on the cathode will continue for a predetermined length of time, and then be discontinued, but will be reinstituted automatically substantially immediately if the current value in the reference circuit is above normal.

Further objects and advantages will be apparent from the following description, reference being had to the acrompanying drawings wherein preferred embodiments of the invention are illustrated.

In the drawings:

Fig. 1 is a diagrammatic representation of one form of the invention;

Fig. 2 is a diagrammatic representation of a combination manual and automatic system employing my invention;

Fig. 3 is a diagrammatic representation of one form of the invention including a field instrument which is utilized for indicating the potential of either of the cathode or the anode-cathode and for rejuvenating the reference half-cell; and

Fig. 4 is a diagrammatic representation of another form of the invention including a more simple field instrument which is utilized for indicating the potential only of the cathode and for rejuvenating the half-cell.

Referring more in detail to the drawings and as an example of the metals used, I show as the cathode a steel plate 21, as the anode-cathode magnesium 22, and as the anode platinum 23. Further, for illustrating one form of the invention, these

metals

21, 22 and 23 are immersed in sea water, the level of which is indicated by the numeral 25. I impress an electric current on the anode-cathode 22 and the cathode 21 through a suitable source of current, and in Fig. 1 this source of current is a direct current generator 26, the current being impressed across the variable resistance 27 through ammeter 28,

lines

29 and 30 through the magnesium 22, through the sea water to the platinum anode 23, and then by Wire 32 to the positive side of the generator. Current is also impressed upon the steel plate 21 from magnesium plate 22 through

Wires

30 and 33, ammeter 34, variable resistance 35, wire 36 to the steel plate 21, and thence by sea water to the plate 22. The variable resistance 27 is adjusted so that the potential of the magnesium is 2105 millivolts, namely, raised 515 millivolts; likewise the variable resistance 35 is adjusted so that the potential at the steel plate 21 is 890 millivolts. These potentials are measured through reference circuits. The reference circuit for the magnesium includes a reference half-cell 38, wire 39, millivoltmeter 40, wire 42, movable switch contact 44, a stationary switch contact 45, wire 46 which is connected to magnesium plate 22 by the wire 30; the circuit is completed through the sea water. The reference circuit for the steel cathode comprises the reference half-cell 38, wire 39, millivoltmeter 40, wire 42, movable switch contact 44, a stationary contact 48, wire 49 which is connected to the steel plate 21 by wire 36; the circuit is completed between the cathode 21 and the reference half-cell 38 through the sea water.

The potentials of the magnesium plate 22 and the steel plate 21 are periodically determined through the aforementioned reference circuits and the

variable resistances

27 and 35 and adjusted to maintain the desired potential on these plates. In the instant example, the steel plate 21 may be the steel hull of a ship and the magnesium may be in the form of plates which are exposed to the sea water but are electrically insulated from the hull of the ship. By maintaining the desired potentials of the hull and of the magnesium, corrosion or dissolution of the metal is prevented.

It has been found, however, that when the reference half-cell is subjected to various environments found in the sea, its resistance to the flow of current is varied, i.e., under certain conditions the reference half-cell 38 becomes negatively polarized and the resultant indication at the millivolt meter 40 is false with respect to the true potential of either the magnesium or the steel. Heretofore it has been the practice to replace the reference half-cell at an extremely high cost due to its location with respect to the ships hull.

In the instant embodiment the reference half-cell is formed of silver-silver chloride. I have discovered that, by connecting the half-cell with the positive side of a source of direct current, the half-cell is depolarized, that is rejuvenated. The circuit for rejuvenating the reference half-cell 38 comprises a battery 51,

stationary contacts

52 and 53 which are arranged to be bridged by contact 54, carried by but insulated from the switch arm 44,

wires

56, 49 and 36, steel plate 21, the sea water, reference half-cell 38 and

wires

39 and 57 to the positive side of the battery.

As shown in Fig. 4, I provide a field instrument for measuring the potential of the cathode 21 and for impressing depolarizing current upon the reference halfcell 38. This instrument includes a casing indicated by dot and dash lines 60, the

wires

49 and 57 being removably connected respectively with the

wires

36 and 39 by conductor clips shown diagrammatically at 61 and 62. The battery, the millivolt meter and the switching mechanism are all contained within this casing. A modification thereof is shown in Fig. 3, in which the instrument is also utilized for measuring the potential of the magnesium plate 22. In this embodiment the wire 46 is removably connected to wire 30 by a clip indicated diagrammatically at 63.

By virtue of the instrument in Fig. 4, the potential of the hull or other cathode can be readily read, and, if below a predetermined minimum, the reference half-cell can be readily rejuvenated. Should the potential still be below normal, the variable resistance 35 is adjusted so that the proper galvanic action takes place between the magnesium and the sea water to increase the potential on the hull 21.

In the embodiment shown in Fig. 3, instead of the generator 26, there is provided a transformer 226 the primary of which is shown at 65 connected with a suitable source of, for example, 110 volt A.C. current, by wire 66 and wire 67, the latter containing a variable resistance 68. The secondary is shown at 70 interposed between the

wires

32 and 33, there being a rectifier 71 in wire 32. In this embodiment the field instrument also provides for the ready measuring of the potential of the magnesium 22. In this embodiment the potential impressed upon the magnesium 22 is governed by adjusting the variable resistance 68.

Referring now to the automatic system shown in Fig. 2,

like in Fig. 3, current is impressed upon the magnesium 22 from the secondary coil 70,

wires

29 and 30, magnesium 22, platinum 23, wire 32 and rectifier 71, and from rectifier 71 to the opposite side of coil 70. Current is normally impressed upon the cathode 21, herein shown as a ships hull, over the circuit including magnesium 22,

wires

30 and 33, ammeter 34, wire 74, stationary contact 75, movable contact 76 of a relay 77, wire 78, a part of variable resistance 35, wire 36, plate 21, and then via the sea water to magnesium 22. The contact 76 is normally maintained closed on contact 74 by a spring 80. In the event that the potential of the cathode 21 is above a predetermined maximum, that part 81 of the variable resistance 35 is reconnected in circuit by breaking the short-circuit through wires 74 and 78. This is accomplished by energizing the coil 77 as hereinafter described. The rectifier 71 impresses a constant, adjustable source of negative current to the magnesium 22, through sea water to platinum 22, through wire 32 to positive side of rectifier.

In this embodiment of the invention, the reference half-cell is indicated at 238. It is connected across meter 83 by wire 84, variable resistance 85, wire 86, coil 88, wire 89 to the ships hull 21 through wire 36, and thence via sea water to the reference half-cell 238. When the reference potential is of a predetermined high value, the arm 91 of the meter will bridge, through contact 92,

contacts

93 and 94. As long as

contacts

93 and 94 are bridged by movable contact 92, a circuit will be completed from the secondary coil 96 of a transformer 97 through wire 98, resistance 99, wire 101,

contacts

94, 92 and 93, wire 102, coil 103 of a relay 104, wire 105, milliammeter 106 and rectifier 107 to the opposite side of the coil 96.

Relay 104 controls two sets of contacts through its armature 109. One set of these contacts, namely, movable contact 110 and stationary contacts 111 and 112, maintains a circuit through the coil 113 of relay 77 and maintains a circuit through the primary coil 114 of a transformer 115. As long as contact 110 is closed on contacts 111 and 112, the circuit for the relay coil 113 is as follows: 110 volt A.C. wire 116, a fuse, wires 117, contacts 112, 110, 111,

wires

118 and 119, coil 113 to the opposite side of the line 120. The circuit is also maintained through the primary coil 114, since it is connected in parallel with coil 113 through wires 122 and 123. Inasmuch as coil 113 is energized, its armature contact 76 is separated from contact 75 and the charging current, for the hull 21, also flows through the coil portion 81 of the variable resistance 35.

As long as coil 103 is energized, the contact 124 on armature 109

bridges contacts

125 and 126 to complete a rejuvenating or depolarizing circuit to the reference halfcell 238; that is, the half-cell 238 is connected to the positive side of a source of current, namely, the positive side of secondary coil 96, the circuit being reference halfcell 238, sea water, cathode 21,

wires

36, 89 and 98, to the negative side of coil 96, thence the current flows via the rectifier 107, milliammeter 106,

wires

105 and 128,

contacts

125, 124 and 126, wire 129, variable resistance 131, and wires 132 and 84 to the reference half-cell 238.

Arm 91 of meter 83 is normally held in contact-closing position by a permanent magnet 134, but can be pushed from that position by a plunger 135. This plunger is actuated by a bellcrank lever 137, and the bellcrank lever is moved in a counterclockwise direction by the solenoid plunger 139 of a solenoid coil 140. Coil 140 is energized by the secondary coil 96 of transformer 97 through the circuit including wire 98, resistance 99, wire 101, coil 140, wire 142, tube 143,

wires

144 and 105, milliammeter 106, rectifier 107 to the opposite side of coil 96. 'The heater 146 of the electronic tube 143 is energized by the secondary winding 147 of transformer 115 through

wires

148 and 149. The construction of the tube 143 is such that, after the heater is brought into operation for a predetermined lengthiof time, the circuit is completed for the solenoid coil 140throughthe tube 143; Thus, after a predetermined time, the plunger 135 will move the arm 91 in a counterclockwise direction, and thereby interrupt the circuit between

contacts

93 and 94, causing deenergization of coil 103 andthe consequent separation of contact 110 from contacts 111 and 112, and the separation of contact 124 from

contacts

125 and 126. When this occurs, the circuit to coil 113 will be interrupted, whereby the resistance portion 81 of variable resistance will be short-circuited through wire 74,,contacts and 76, and wire 78. ,Also, the separation'of contact 124 from

contacts

125 and 126 will cause interruption of the depolarization ofthe reference half-cell 238.

Should the. potential across the reference circuit be above a predetermined maximum, the arm 91 of the meter 83 willtend immediately to complete the bridging of contacts 93 and 94:. However, the plunger will prevent the bridging of these contacts until after a predetermined cooling time of the electronic tube 143, that is,

until the circuit through coil is interrupted, whereby the plunger 135 is retracted to permit the closing of contact 92, on

contacts

93 and 94. Should the potentialin thereferencecircuit be below a predetermined high value,

the short-circuit of the coil portion 81 will be maintained. M

Inasmuch as the reference half-cell is substantially constantly intermittently subjected to depolarization, its reference character is maintained sufiiciently constant to withstand any environment to which it is subjected. Obviously, should the silver-silver chloride, reference halfcell 238 become polarized, such polarization causes such resistance in the reference circuit as to cause the armature contact 92, of the meter 83, to remain out of contact with

contacts

93 and 94 until the current from the magnesium raises the polarization of the cathode 21 to a corresponding value, as previously explained.

' Referring again to Fig. 2, the transformer 97 also includes a primary coil 151 which is connected across a source of 110 volt A.C. current by wires 152 and 153.

Mechanism is also provided for visually indicating the potential of the hull or cathode 21 while the automatic mechanism is functioning, for manually impressing a positive current upon a second reference half-cell $3, for manually determining the hull potential and for manually determining the magnesium potential. For this purpose there is provided a switch 155 including four

conductor sectors

156, 157, 158 and 159, all connected and movable simultaneously through a shaft shown in dot and dash lines at 160. This switch has five positions, which are indicated ata, b, c, d and e, a being the off position, and all of these sectors are shown in the off position. When the switch is in the e position, which position is preferably maintained during automatic operation, the potential of the hull can be determined through the milli voltmeter through the following circuit: Reference half-- cell 238,

wires

84, 132, 162,. a stationary contact 163, sector 156, stationary contact 164, wire 165, variable resistance portion 167 of variable resistance 166, millivoltmeter 46,

wires

168 and 169, stationary contact 1711, sector 157, stationary contact 172,

wires

173 and 36 to the cathode 21, and thence by the water to half-cell 238. Thus the potential of the cathode can always be determined at the millivoltmeter 40 while the system is under automatic operation.

Under manual operation, and when it is desirable to rejuvenate reference half-cell 33, the switch 155 is moved to the b position. When in this position, the current flow can be traced from reference half-cell 38 through

wires

39 and 57 to the positive side of the dry cell 51, and from the negative side of the battery 51 through wire 175, stationary contact 176, sector157, stationary contact 172, and

wires

173 and 36 to the cathode 21, and thence from the cathode 21 to the reference half-cell 38 through the water. At this time, the value of'current flow can be determined through the following circuit: Positive battery 51, wire 178, stationary contact 179, sector 156, stationary contact 164, wire portion 167 of variable resistance 166, millivoltmeter 41), wires 168 and 181), stationary contact 181, sector 153, stationary contact 182, wires 153 to negative battery51.

Under manual operation, the hull potential can be determined at the millivoltmeter it? when the switch 155 is moved to the 0 position. This circuit can be traced as follows: Half-cell 35,

wires

57, 178 and 184, stationary contact 185, sector 156, stationary contact 164, wire 165, variable resistance portion 167, meter 16, wires 168 and 136, stationary contact 138, sector 157, contact 172, and

wires

173 and 36 to the cathode 21, thence through the water to the half-cell 38.

The magnesium potential can be determined when switch 155 is in the d position, the circuit therefor being as follows: Half-cell 38, wire 39, portions and 167 of variable resistance 166, meter 46,

wires

168 and 191, stationary contact 192, sector 159, stationary contact 193,

wires

194, 29 and 36 to magnesium 22, and thence. by the water to the half-cell 38.

It will be observed that contact 164 is in constant con-- tact with sector 1156, contact 172 in constant contact with sector 157, contact 182 in constant contact with sector 158, and contact 193 in constant contact with sector 159.

It should be pointed out here that either the reference half-

cell

33 or 238 can be depolarized, as above explained, while the system is used in sea water, fresh water, or distilled water; that is, silver chloride is formed on the reference half-cell while being subject to positive current and when used in sea water, fresh water, or distilled water.

The resistance offered by 99' is in the nature of 120 ohms. It will be observed that a capacitor is connected across the secondary winding of the transformer 97, the circuit therefor being Wire 98, resistance 99, wire 196, capacitor 197, and

wires

198 and 105, milliammeter 106, and rectifier 107. By utilizing the capacitor 197 as herein shown, a relatively small, low value transformer 97 may be employed, the capacitor providing sufficient current for actuating the heavy duty coil 163;.

Thus it is apparent from the foregoing description that I have provided for the automatic rejuvenation or depolarization of a reference half-cell and have provided I for the automatic maintaining of the desired potential at the cathode. T 00, in the event of failure of the automatic system, I have provided for the constant impressing of current on the cathode and the anode-cathode 22, the circuit therefor being magnesium 22,

wires

30 and 33, ammeter 34, resistance 35, wire 36, cathode 21, thence by water to the magnesium 22 and simultaneously current from the negative side of the rectifier 71 through coil 70,

wires

29 and 36 to magnesium 22, through water to platinum 23, to positive side of rectifier 71. Also, during manual operation, the potential of either the cathode or the anode-cathode can be determined. A positive current can also be impressed upon the reference half-cell 38 to depolarize or rejuvenate the same.

While the forms of embodiments herein shown and described constitute preferred forms, it is to be understood that other forms may be adopted falling Within the scope of the claims that follow.

I claim:

1. In an electrolytic system for cathodic protection of the type which includes an electrolyte, a cathode and an anode adapted to be disposed in the electrolyte, means connecting the cathode to the anode to permit current flow between the same, reference half cell means of the silversilver chloride type adapted to be disposed in the electrolyte, means connecting the reference means to the cathode, the reference means having a normal potential substantially lower than the potential on the cathode so that there is a current flow between the reference half cell means and the cathode, the reference half cell means .the same.

2. In an electrolytic system for cathodic protection of the type which includes an electrolyte, an electrode adapted to be disposed in the electrolyte, reference half cell means of the silver-silver-chloride type adapted to be disposed in the electrolyte, means connecting the reference half cell means to the electrode to permit current fiow between the same, the reference half cell means having a normal potential substantially lower than the potential on the electrode, the reference half cell means being characterized by a tendency to become polarized in one polarity during current flow between it and the electrode, and means for applying a voltage of opposite polarity to said reference half cell means to cause current flow in an opposite direction to depolarize the same.

3. An electrolytic system as in claim 2 wherein said means connecting the reference half cell means to the electrode includes means for measuring the potential difierence between the reference half cell means and the electrode.

4. In an electrolytic system for cathodic protection of the type which includes an electrolyte, a cathode, and an anode adapted 'to be'd-isposed in the electrolyte, means connecting the cathode to the'anode to permit current 7 flow between the same, reference half cell means adapted to be disposed in the electrolyte means connecting the reference half cell means to the cathode, the reference half cell having a normal potential substantially lower;- than the potential on the cathode, the reference halfcell means being characterized by a tendency to become polarized negatively during current flow in one direction between it and the cathode, and means for applying a. voltage of positive polarity to said reference half cell,

means to cause a current flow in an opposite direction between it and the cathode to de-polarize the same.

References Cited in the file of this patent UNITED STATES PATENTS Polin Nov. 19, 1935 Hersch Sept. 3, 1957 a

Claims

1. IN AN ELECTROLYTIC SYSTEM FOR CATHODIC PROTECTION OF THE TYPE WHICH INCLUDES AN ELECTROLYTE, A CATHODE AND AND ANODE ADAPTED TO BE DISPOSED IN THE ELECTROLYTE, MEANS CONNECTING THE CATHODE TO THE ANODE TO PERMIT CURRENT FLOW BETWEEN THE SAME, REFERENCE HALF CELL MEANS OF THE SILVERSILVER CHLORIDE TYPE ADAPTED TO BE DISPOSED IN THE ELECTROLYTE, MEANS CONNECTING THE REFERENCE MEANS TO THE CATHODE, THE REFERENCE MEANS HAVING A NORMAL POTENTIAL SUBSTANTIALLY LOWER THAN THE POTENTIAL ON THE CATHODE SO THAT THERE IS A CURRENT FLOW BETWEEN THE REFERENCE HALF CELL MEANS AND THE CATHODE, THE REFERENCE HALF CELL MEANS BEING CHARACTERIZED BY A TENDENCY TO BECOME POLARIZED IN ONE POLARITY DURING CURRENT FLOW BETWEE IT AND THE CATHODE, AND MEANS FOR APPLYING A VOLTAGE OF OPPOSITE POLARITY TO SAID REFERENCE HALF CELL MEANS TO DEPOLARIZE THE SAME.