US3878064A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and apparatus for measuring pitting corrosion tendencies
Assignee: Veolia WTS USA Inc
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Filing: 1973-07-27
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Granted: 1975-04-15
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Expires: 1993-07-27
Abstract
Abstract A Cathode, an Anode wrapped in filter paper or other barrier to oxygen diffusion, a Reference Electrode (and optionally an Auxiliary Electrode) are placed in an aerated electrolytic liquid. The open circuit potential between the Cathode and Reference Electrode is impressed upon a capacitor. By means of a two-position switch an operational amplifier then causes the potential of the anode, in a circuit including the Reference Electrode, Auxiliary Electrode (or the electrode previously used as the Cathode) and an Ammeter, to become equal to the open circuit cathode-reference electrode potential impressed upon the capacitor. The amplifier provides the necessary current of either polarity to achieve the equality. The polarizing current flowing through the Ammeter is read and a qualitative indication of the pitting tendency is obtained.
Inventors
- 👤 Aaron Weisstuch
- 👤 Iii Charles E Schell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 10:52
CPC Classifications
G; G01; G01N; G01N17/00; G01N17/02
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
189 words
A METHOD OF MEASURING THE PITTING CORROSION TENDENCY OF METAL EXPOSED TO AN ELECTROLYTIC LIQUID, COMPRISING: A. PLACING A FIRST AND A SECOND ELECTRODE IN THE ELECTROLYTIC LIQUID WHEREIN ACESS TO OXYGEN IS UNRESTRICTED, SAID ELECTRODES HAVING AN OPEN CIRCUIT POTENTIAL THEREBETWEEN B. STORING THE OPEN CIRCUIT POTENTIAL ON A STORAGE MEANS, C. DISCONNNECTING THE FIRST ELECTRODE FROM THE STORAGE MEANS AND CONNECTING A THIRD ELECTRODE TO WHICH OXYGEN ACCESS IS RESTRICTED THERETO, SAID THIRD ELECTRODE BEING IN THE LIQUID AND THE ONLY ELECTRODE TO WHICH OXYGEN ACCESS IS RESTRICTED, D. PLACING A FOURTH ELECTRODE IN THE LIQUID, E. CONNECTING THE FOURTH ELECTRODE IN A CIRCUIT INCLUDING THE SECOND ELECTRODE UPON DISCONNECTING OF THE FIRST ELECTRODE AND CONNECTING OF THE THIRD ELECTRODE TO THE STORAGE MEANS, F. CAUSING THE POTENTIAL OF A CIRCUIT INCLUDING THE THIRD ELECTRODE, THE FOURTH ELECTRODE AND THE STORAGE MEANS TO EQUAL THE POTENTIAL INITIALLY STORED ON THE STORAGE MEANS, AND G. MEASURING THE CURRENT REQUIRED TO CAUSE THE POTENTIAL OF THE CIRCUIT INCLUDING THE THIRD ELECTRODE TO EQUAL THE POTENTIAL OF THE CIRCUIT INCLUDING THE FIRST ELECTRODE WHEREBY THE PITTING CORROSION TENDENCY IS ASCERTAINED.
Claim 2
Independent Claim
189 words
A METHOD OF MEASURING THE PITTING CORROSION TENDENCY OF METAL EXPOSED TO AN ELECTROLYTIC LIQUID, COMPRISING: A. PLACING A FIRST AND A SECOND ELECTRODE IN THE ELECTROLYTIC LIQUID WHEREIN ACESS TO OXYGEN IS UNRESTRICTED, SAID ELECTRODES HAVING AN OPEN CIRCUIT POTENTIAL THEREBETWEEN B. STORING THE OPEN CIRCUIT POTENTIAL ON A STORAGE MEANS, C. DISCONNNECTING THE FIRST ELECTRODE FROM THE STORAGE MEANS AND CONNECTING A THIRD ELECTRODE TO WHICH OXYGEN ACCESS IS RESTRICTED THERETO, SAID THIRD ELECTRODE BEING IN THE LIQUID AND THE ONLY ELECTRODE TO WHICH OXYGEN ACCESS IS RESTRICTED, D. PLACING A FOURTH ELECTRODE IN THE LIQUID, E. CONNECTING THE FOURTH ELECTRODE IN A CIRCUIT INCLUDING THE SECOND ELECTRODE UPON DISCONNECTING OF THE FIRST ELECTRODE AND CONNECTING OF THE THIRD ELECTRODE TO THE STORAGE MEANS, F. CAUSING THE POTENTIAL OF A CIRCUIT INCLUDING THE THIRD ELECTRODE, THE FOURTH ELECTRODE AND THE STORAGE MEANS TO EQUAL THE POTENTIAL INITIALLY STORED ON THE STORAGE MEANS, AND G. MEASURING THE CURRENT REQUIRED TO CAUSE THE POTENTIAL OF THE CIRCUIT INCLUDING THE THIRD ELECTRODE TO EQUAL THE POTENTIAL OF THE CIRCUIT INCLUDING THE FIRST ELECTRODE WHEREBY THE PITTING CORROSION TENDENCY IS ASCERTAINED.
Claim 3
Dependent Claim
14 words
A method as defined in claim 1 wherein the storage means is a capacitor.
Claim 4
Dependent Claim
15 words
A method as defined in claim 1 including switching the first electrode between said circuits.
Claim 5
Dependent Claim
26 words
A method as defined in claim 1 including placing a high input impedance operational amplifier in said second circuit for causing said potentials to be equal.
Claim 6
Dependent Claim
25 words
A method as defined in claim 1 including directly grounding the third electrode to eliminate cable IR drop from the cIrcuits including the third electrode.
Claim 7
Dependent Claim
33 words
A method as defined in claim 1 wherein said first electrode is a cathode, said second electrode is a reference, said third electrode is an anode, and said storage means is a capacitor.
Claim 8
Dependent Claim
139 words
A pitting corrosion tendency measuring apparatus comprising: a. an anode to which oxygen access is restricted, b. a cathode to which oxygen access is unrestricted, c. a reference electrode to which oxygen access is unrestricted, d. an auxiliary electrode to which oxygen access is unrestricted, e. a storage means, f. means for connecting said storage means, cathode and reference electrode in a circuit to store the open circuit potential on said storage means, g. means for switching said storage means into a circuit including said anode and said auxiliary electrode, h. means for causing the potential of the circuit including the anode and auxiliary electrode to equal the potential initially stored on the storage means, and i. an ammeter means for measuring the current required to reach said equal potential, said auxiliary electrode being in series with said ammeter.
Claim 9
Dependent Claim
139 words
A pitting corrosion tendency measuring apparatus comprising: a. an anode to which oxygen access is restricted, b. a cathode to which oxygen access is unrestricted, c. a reference electrode to which oxygen access is unrestricted, d. an auxiliary electrode to which oxygen access is unrestricted, e. a storage means, f. means for connecting said storage means, cathode and reference electrode in a circuit to store the open circuit potential on said storage means, g. means for switching said storage means into a circuit including said anode and said auxiliary electrode, h. means for causing the potential of the circuit including the anode and auxiliary electrode to equal the potential initially stored on the storage means, and i. an ammeter means for measuring the current required to reach said equal potential, said auxiliary electrode being in series with said ammeter.
Claim 10
Dependent Claim
14 words
An apparatus as defined in claim 7 wherein said storage means is a capacitor.
Claim 11
Dependent Claim
14 words
An apparatus as defined in claim 7 wherein said anode and cathode are steel.
Claim 12
Dependent Claim
32 words
An apparatus as defined in claim 7 wherein said causing means includes an operational amplifier having one input connected to said storage means and a second input connected to said reference electrode.
Claim 13
Dependent Claim
21 words
An apparatus as defined in claim 7 including means for eliminating cable IR drop between said anode and said measuring means.
Claim 14
Dependent Claim
17 words
An apparatus as defined in claim 11 wherein said eliminating means includes means for grounding said anode.
Claim 15
Dependent Claim
158 words
A pitting corrosion tendency measuring apparatus comprising: a. an anode to which oxygen access is restricted, b. a cathode to which oxygen access is unrestricted, c. a reference electrode to which oxygen access is unrestricted, d. a capacitor, e. means for connecting said capacitor, cathode and reference electrode in a circuit through a pair of double pole switches to store the open circuit potential on said capacitor, f. said switches switching said capacitor into a circuit including said anode, g. means for causing the potential of the circuit including the anode to equal the potential initially stored on the capacitor, said causing means including an operational amplifier having a pair of input terminals and an output terminal, each input terminal connected to a pole of one of said switches, one of said input terminals also being connected to said capacitor, h. an ammeter connected to said output terminal for measuring the current required to reach said equal potential.
Claim 16
Dependent Claim
158 words
A pitting corrosion tendency measuring apparatus comprising: a. an anode to which oxygen access is restricted, b. a cathode to which oxygen access is unrestricted, c. a reference electrode to which oxygen access is unrestricted, d. a capacitor, e. means for connecting said capacitor, cathode and reference electrode in a circuit through a pair of double pole switches to store the open circuit potential on said capacitor, f. said switches switching said capacitor into a circuit including said anode, g. means for causing the potential of the circuit including the anode to equal the potential initially stored on the capacitor, said causing means including an operational amplifier having a pair of input terminals and an output terminal, each input terminal connected to a pole of one of said switches, one of said input terminals also being connected to said capacitor, h. an ammeter connected to said output terminal for measuring the current required to reach said equal potential.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |