Process for removal of chloride ions from steel surfaces

Details Process for removal of chloride ions from steel surfaces Process for removal of chloride ions from steel surfaces

2000-06-20

2002-07-30

Phasge, Arun S. (Department: 1741)

Electrolysis: processes, compositions used therein, and methods

Electrolytic material treatment

Metal or metal alloy

C205S710000, C205S711000, C205S717000, C205S724000, C205S731000, C205S734000, C205S735000

Reexamination Certificate

active

06425997

ABSTRACT:

BACKGROUND AND FIELD OF INVENTION
This application relates to corroded and pitted steel surfaces and the removal and measurement of chloride ions present thereon, which ions are known to promote corrosion of steel surfaces.
RELATED ART
Chloride ions an known to accelerate the corrosion on of steel surface (Publ. Ref. 1). Before a steel surface is painted, it is desirable to know whether chloride ions are present and their contamination level since painting over chloride ions will allow corrosion to proceed under the paint coat (Publ. Ref. 2). As little as 10 &mgr;g. chloride ion per square cm. of steel surface will accelerate the corrosion of steel surfaces (Publ. Ref. 3).
Chloride ion contamination of steel surfaces is a widespread problem caused by circumstances as diverse as the ocean shipping of steel and the use of salt on road surfaces such as bridges in winter.
Drastic steps, such as sandblasting of steel surfaces, often are used to remove corrosion products and chlorides prior to painting. However, one sandblasting step often is not enough to remove all the chloride ions, and rapid corrosion after sandblasting can occur overnight under humid conditions (Publ. Ref. 4).
In addition to the prevalence of chloride contamination of steel surfaces and the difficulty of removing chloride ion contamination, it is also difficult to obtain a valid measurement of the concentration level of chloride ions present on a steel surface.
Bresle Sampler
The Swedish Fire Research Laboratory (Brandforsk) developed a means of measuring chloride contamination with a Bresle Sampler (Publ. Ref 5). The Sampler is configured to be adhered to a surface with a cavity of known dimension and volume. Distilled or deionized water is injected into the cavity by syringe needle through a rubbery film. Removal of the water after one minute contact is also accomplished with a syringe needle. The water removed is analyzed by chemical reagents for its chloride content using reagents included in the Bresle Kit. Chloride contamination after fires occurs by formation of hydrogen chloride through burning of polyvinylchloride plastics and other chlorine-containing plastics.
While the Bresle Sampler is useful for removing readily extracted chlorides from steel surfaces Boocock has shown that not all chlorides arm removed from corroded and pitted steel surfaces by water washing and includes data obtained with a Bresle Sampler (Publ. Refs 6 and 7).
Flores (Publ. Ref. 8) also studied the performance of the Bresle Sampler.
While the reason for the difficulty of completely extracting chloride ions by water washes is not known for a certainty, it is believed to be caused by a phenomenon described as “Electrolytic Confinement,” which will be described later.
“Elcometer
134
”
In January 1999, a new test method for chlorides became known to applicant through commercial literature issued by KTA Tator, Inc. as new instrument offerings (Publ. Ref. 9).
Literature printed by Elcometer, Inc., 1893 Rochester Industrial Drive, Rochester Hills, Mich. 48309-3342 (Publ. Ref. 10) describes the testing process a follows in the brochures on “Elcometer
134
” and the “CHLOR*TEST.”
1. Empty the entire contents of the CHLOR*EXTRACT™ container into the CHLOR*SLEEVE™. Peel off the protective backing, pinch the sleeve to expel some of the air and adhere the sleeve to the surface to be tested.
2. Massage the extract against the surface; then peel the sleeve off the surface and place it in the perforated hole in the box lid.
3. Snap the sealed ends off the glass tube, insert it into the sleeve and down into the extract. In about two minutes read the color change to identify the chloride level in both parts per million and micro grams per centimeter squared; the ratio is 1:1.
Applicant does not know of any publication which has measured the efficiency of extraction of chlorides from standard rusted panels using the “Elcometer
134
” test method.
It is clear that “Elcometer
134
” is not an electrochemical test meter, but is a chemical method using an extraction solution and a Kitagawa absorbent tube for chloride measurement.
BACKGROUND OF THE INVENTION
I am aware of the following Prior Art:
U.S. Pat. No.
INVENTOR
ISSUED
CLASS
3,491,012
Winslow
1/20/70
204/195
3,497,442
Vincent
2/24/70
204/195
3,710,237
Watson et al.
1/09/73
324/446
3,808,523
Jobe
4/30/74
324/446
3,829,761
Shimizu et al.
8/13/74
324/30B
3,830,480
Grant
8/20/74
266/34LM
3,849,723
Allen
11/19/74
324/30R
3,850,736
Seyl
11/26/74
204/195C
3,878,064
Weisstuch et al.
4/15/75
204/IT
3,953,790
Ebling et al.
4/27/76
324/446
4,019,133
Manley et al.
4/19/77
324/65CR
4,032,296
Hall
6/28/77
422/89
4,101,828
Dehler
7/18/78
324/65R
4,181,882
Issacs et al.
1/01/80
324/71R
4,226,693
Maes
10/07/80
204/195C
4,238,298
Tsuru et al.
12/09/80
204/IT
4,331,923
Akers, Jr.
5/25/82
324/449
4,362,994
Goldsmith et al.
12/07/82
324/449
4,383,221
Morey et al.
5/10/83
324/439
4,395,318
Tait et al.
7/26/83
202/404
4,427,945
Sperry, III
6/12/84
324/446
4,454,006
Hausler et al.
6/12/84
205/776
4,563,427
Weiss et al.
1/07/86
436/6
4,800,165
Oka et al.
1/24/89
436/6
4,806,849
Kihira et al.
2/21/89
324/65CR
4,833,413
Head
5/23/89
324/449
4,962,360
Homma et al.
10/09/90
324/700
5,139,627
Eden et al.
8/18/92
205/775.5
5,188,715
Chen et al.
2/23/93
205/776
5,194,814
D'Couto
3/16/93
324/446
5,221,893
Kondou et al.
6/22/93
324/71.2
5,266,899
Bull et al.
11/30/93
324/439
5,286,257
Smart el al.
2/15/94
204/153.11
5,306,414
Glass et al.
4/26/94
204/404
5,310,470
Agarwala et al.
5/10/94
204/404
5,316,633
Sakal et al.
5/31/94
204/153.11
5,437,773
Glass el al.
8/01/95
204/153.11
5,483,166
Olsen
1/09/96
324/450
5,543,717
Kordas
8/06/96
324/444
5,553,426
Tiefnig
12/10/96
324/700
5,674,375
Thompson
10/07/97
205/734
PRIOR ART CONDUCTIVITY CELL PATENTS
Of the Patents Listed Above, the Following Patents Describe Conductivity Cells and their Use:
U.S. Pat. No. 3,497,442
U.S. Pat. No. 3,710,237
U.S. Pat. No. 3,808,523
U.S. Pat. No. 3,829,761
U.S. Pat. No. 3,849,723
U.S. Pat. No. 3,953,790
U.S. Pat. No. 4,032,296
U.S. Pat. No. 4,331,923
U.S. Pat. No. 4,362,994
U.S. Pat. No. 4,383,221
U.S. Pat. No. 4,427,945
U.S. Pat. No. 4,833,413
U.S. Pat. No. 5,194,814
U.S. Pat. No. 5,266,899
U.S. Pat. No. 5,543,717
U.S. Pat. No. 5,483,166
U.S. Pat. No. 5,612,622
None of the above patents describes a conductivity cell for measuring chloride ions on rusted steel. U.S. Pat. No. 4,331,923 employs a low amplitude AC square wave current to measure conductivity while U.S. Pat. No. 5,543,717 uses a rectangular waveform and mentions use of sine waves for conductivity measurement. Although such waveforms are generally similar to the waveforms employed with the Johnson Cell (J-Cell) of this invention to release chloride Ions and to measure conductivity, none of the above patents employs a high frequency waveform in a pre-measurement step to free chloride ions from rusted steel.
While alternating current and/or impedance have been employed to measure corrosion in the following US patents, none of these patents mentions use of high frequency alternating current of any waveform being used to free chloride ions from corroded steel surfaces, nor is the any mention of its use to wash away chloride ion contamination from steel surfaces when employed with a flowing stream of water as described in the Embodiment of our invention.
PRIOR ART PATENTS ON CORROSION EMPLOYING ALTERNATING CURRENT
U.S. Pat. No. 4,019,133
U.S. Pat. No. 4,181,852
U.S. Pat. No. 4,238,298
U.S. Pat. No. 4,800,165
U.S. Pat. No. 4,806,849
U.S. Pat. No. 4,962,360
U.S. Pat. No. 5,221,893
U.S. Pat. No. 5,583,426
OTHER PRIOR ART PATENTS
The Remaining Patents in Prior Art are Briefly Described Below:
U.S. Pat. No. 3,491,012: Describes a means of refinishing a pitted electrode assembly while maintaining equal areas in the electrodes used.
U.S. Pat. No. 3,830,480: Sampler for molten metal to measure metal temperature and its gaseous content.
U.S. Pat. No. 3,850,736: Device for catholically polarizing two duplicated electrodes with substantially no interference with corrosion current measurement with sai

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