US4950453A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Inhibiting corrosion by water
Assignee: Individual
•
Filing: 1989-05-01
•
Granted: 1990-08-21
•
Expires: 2009-05-01
Abstract
Abstract There is disclosed a method for the protection of metal surfaces against corrosion by the formation of a passivating coating of zinc silicate on the surfaces of the metals exposed to the water. The metal surfaces are preconditioned by contact with water containing a soluble zinc salt in an amount from about 0.5 to about 5 parts zinc per million weight parts of the water while the total alkalinity is maintained above 100 millequivalents by the addition of a water soluble alkaline material, as needed. The pretreatment passivates the metal surfaces with a coating of zinc carbonate, as can be determined by measuring the magnitude of external current flow between electrodes of a test probe maintained in the water. When the metal has been coated with a film of zinc carbonate, typically after a few days to a week, the addition of the zinc salt is ceased, and a water soluble silicate, particularly sodium orthsilicate or sodium metasilicate is added to the water in an amount from about 1 to 10 parts per million of silicate. The addition of this silicate effectively deposits a protective coating of zinc silicate on the surfaces of the metal subjected to corrosion, particularly the surfaces of cathodic metals.
Inventors
- 👤 W. Bruce Murray
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 19:56
CPC Classifications
C; C23; C23C; C23C22/00; C23C22/05; C23C22/68; C23F; C23F11/00; C23F11/08; C23F11/18; C02; C02F; C02F1/00; C02F1/68; C02F2303/00; C02F2303/08
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
181 words
A method for the treatment of municipal water to prevent corrosion of metallic equipment and surfaces in contact with water, which comprises: a. adding to said water a water soluble zinc salt in an amount from 0.5 to about 5 parts zinc per million weight parts of water, and exposing said surfaces to said water containing said water soluble zinc salt; b. adding to said water, a water soluble alkaline material selected from the group consisting of sodium carbonate, sodium hydroxide, calcium hydroxide, and mixtures thereof, in an amount, as necessary to maintain the total alkalinity of the water above 100 milligrams per liter; c. maintaining said exposure of said surfaces to said water for a sufficient period of time to passivate said surfaces with a coating of zinc carbonate on said surfaces; d. thereupon ceasing the addition of said water soluble zinc salt, and adding to said water a water soluble silicate selected from the class consisting of sodium orthosilicate, sodium metasilicate, and mixtures thereof in an amount from 1 to about 10 parts per million weight parts of water.
Claim 2
Independent Claim
181 words
A method for the treatment of municipal water to prevent corrosion of metallic equipment and surfaces in contact with water, which comprises: a. adding to said water a water soluble zinc salt in an amount from 0.5 to about 5 parts zinc per million weight parts of water, and exposing said surfaces to said water containing said water soluble zinc salt; b. adding to said water, a water soluble alkaline material selected from the group consisting of sodium carbonate, sodium hydroxide, calcium hydroxide, and mixtures thereof, in an amount, as necessary to maintain the total alkalinity of the water above 100 milligrams per liter; c. maintaining said exposure of said surfaces to said water for a sufficient period of time to passivate said surfaces with a coating of zinc carbonate on said surfaces; d. thereupon ceasing the addition of said water soluble zinc salt, and adding to said water a water soluble silicate selected from the class consisting of sodium orthosilicate, sodium metasilicate, and mixtures thereof in an amount from 1 to about 10 parts per million weight parts of water.
Claim 3
Dependent Claim
24 words
The method of claim 1 wherein step b is continued throughout the addition of said water soluble silicate to said water in step d.
Claim 4
Dependent Claim
49 words
The method of claim 1 which comprises monitoring the corrosion characteristic of said water with a corrosion cell comprising an anode electrode and cathode electrode and measuring the external cell current flow between said electrodes during step c to determine when said metal surfaces become passivated in step c.
Claim 5
Dependent Claim
38 words
The method of claim 1 which comprises monitoring the corrosion characteristic of said water with a corrosion cell comprising an anode electrode and cathode electrode and measuring the external cell current flow between said electrodes during step d.
Claim 6
Dependent Claim
30 words
The method of claim 4 which comprises the steps of discontinuing step d and resuming steps a through c when the external cell current flow exceeds a predetermined maximum value.
Claim 7
Dependent Claim
33 words
The method of claim 1 which includes the step of analysis of the water prior to treatment for total alkalinity to determine when the addition of a water soluble alkaline material becomes necessary.
Claim 8
Dependent Claim
18 words
The method of claim 6 wherein said analysis of water for total alkalinity is repeated after said treatment.
Claim 9
Dependent Claim
53 words
The method of claim 1 wherein the amount of water soluble zinc salt to be added to the water during step a is determined by titrating aliquot portions of said water with standard solutions of said water soluble zinc salt to an end point observed as the formation of cloudiness in said water.
Claim 10
Dependent Claim
39 words
The method of claim 8 wherein the amount of zinc salt added in step a is from 0.2 to about 0.7 parts per million of water less than that amount determined by titration to cause cloudiness in said water.
Claim 11
Dependent Claim
16 words
The method of claim 8 wherein said water soluble silicate is selected to be sodium metasilicate.
Claim 12
Dependent Claim
17 words
The method of claim 1 wherein said water soluble zinc salt is selected to be zinc chloride.
Claim 13
Dependent Claim
16 words
The method of claim 1 wherein said water soluble silicate is selected t be sodium metasilicate.
Claim 14
Dependent Claim
16 words
The method of claim 1 wherein said water soluble silicate is selected to be sodium orthosilicate.
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) | 1993-08-20 | 1994-02-19 | 1994-08-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-08-20 | 1998-02-19 | 1998-08-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-08-20 | 2002-02-19 | 2002-08-21 | $7700.00 | Window Closed / Lapsed |