Title of Invention

A METHOD FOR POLY PHOSPHATE COATING ON ROLLED STEEL SHEET TO RESIST CORROSION

Abstract Cold rolled/hot rolled steel sheets are fed into a degreasing bath in order to remove oil, dirts etc. from the surface. Then, the poly-phosphate coating solution in applied on the rolled sheets surface by spraying or the rolled steel sheets are immersed in bath containing poly-phosphate rolled coating solution. Rolled steel sheets with poly-phosphate coating adherence are then rubber squeezed and send to chamber for drying at a temperature of 40°-60°C. The poly-phosphate coated rolled sheets thus obtained were characterized with respect to corrosion, co-efficient of friction, coating uniformity, coating weight and organic molecular net work in the coating.
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FIELD OF THE INVENITON
The present invention generally relates to a method of coating a layer on cold rolled or hot rolled steel sheets applicable in Industrial and domestic use. More particularly the invention relates to a method for improve coating of poly phosphate on roiled steel sheets to resist corrosion effect in poly-season climatic atmosphere.
BACKGROUND OF THE INVENTION
In typical steel plant rolled steel sheets are produced from billets or slabs by rolling, are then fed into a sheet storage stock yard in open atmosphere. The rolled steel sheet from stock yard are delived to customer premises by a suitable transport either by railway wagons or a suitable mode of surface transport through open atmosphere. The moist in the atmosphere

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react with iron particle of steel sheet and formation of rust takes place on the surface of the steel sheet. The rust particles have to be cleaned before proceed to subsequent operation and create problem in industrial productivity for next user.
A prior art discloses that a oiled CRCA sheet after collecting from cold rolling mill, it was immersed into degressing bath in order to remover oil, dirt etc from the surface. The poly-phosphate coating solution was applied on sheet surface by rubber squeeze roll and followed by drying. The poly-phosphate steel sheets were tested in the laboratory to find out the characterized features like corrosion resistance, coating uniformity, coating weight and organic molecular network.
The corrosion resistance properties of the poly-phosphate coated sheets were evaluated in Humidity chamber as per Quakar specification. It was observed that the surface was covered with 40% of red rust after 115 days

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The coating uniformity, organic molecular network in the coating were checked through scanning electron microscope. It was observed that coating was not uniform throughout the surface and molecular network was not found existing and coating layer was 150mg/sqft
To overcome the above corrosion problem on rolled steel sheet an emphasise was made to introduce an improved method of application of modified poly-phosphate coating layer on the rolled steel sheet to avoid rust formation during poly-season climatic atmosphere adaptable before storing in stock yard and despatch from the steel plant.
OBJECT OF THE INVENTION
It is therefore, an object of the present invention to propose a method for improved poly-phosphate coating on rolled steel sheet to resist corrosion effect in poly-season climatic atmosphere which eliminates the disadvantages of prior art.
A further object of the present invention is to propose a method for improved poly-phosphate coating on rolled steel sheet to resist

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corrosion effect in poly-season climatic atmosphere which is easy to access in production process and the coating materials lasts for along period.
A still further object of the present invention is to propose a method for improved poly-phosphate coating on rolled steel sheet to resist corrosion effect in poly-season climatic atmosphere which imparts in increasing paintability, weidabilty and impart in decreasing co-efficient of friction.
An yet further object of the present invention is to propose a method for improved poly-phosphate coating on rolled steel sheet to resist corrosion effect in poly-season climatic atmosphere which provides cost economy.
BRIEF SUMMARY OF THE INVENTION
Cold rolled/hot rolled steel sheets are fed into a degreasing bath in order to remove oil, dirts etc. from the surface. Then, the poly-phosphate coating

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solution in applied on the rolled sheets surface by spraying or the roiled steel sheets are immersed in bath containing poly-phosphate rolled coating solution. Rolled steel sheets with poly-phosphate coating adherence are then rubber squeezed and send to chamber for drying at a temperature of 40°-60°C. The poly-phosphate coated rolled sheets thus obtained were characterized with respect to corrosion, co-efficient of friction, coating uniformity, coating weight and organic molecular net work in the coating.
The coating durability was evaluated and the poly-phosphate sheets were folded in a polyethylene sheet is kept inside humidity chamber maintaining the humidity cycle of 50 degree centigrade temperature and 95% R/H for 30 days. After 30 days exposure, It was observed that only a few rust sposts appeared on the surface. The corrosion resistance performance was found to be significantly superior compared to the oiled sampled.
This coating was distributed uniformly over the surface. This was unlike crystalline structure. This is the polymer net working structure. The

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polymer matrix was found exciting in delaying the diffusion of moisture into the substrate as compare to conventional phosphate coating.
The poly-phosphate coating was observed and found a lining between 170 to 205 mg/sq ft as against a minimum of 150 mg/sq ft. which satisfy the customer profusely beyond their expectation. Besides that there was no problem in welding and sheets passed 500 Hrs of salt spray test without paint delamination. Hence, paintability in good.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure-1- Shows a schematic diagram of a process of poly-phosphate Coating by spray technique.
Figure-2- Shows a schematic diagram of a process of poly-phosphate coating by immersion technique.

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DETAILS DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
As shown in figure-1- A poly phosphate coating solution containing poly phosphate are sprayed from a spray gun (1) on a moving bare rolled sheet (2). For uniform coating, solution leveling the rolled steel sheet are passed through two laveller (3,4) and excess solution fall on a bath (9) placed beneath the spray gun (1). The moving rolled steel sheet coated with poly phosphate coating solution are further squeezed by means of two rubber rollers (5,6). After passing from rubber squeezers (5,6), the laminated poly phosphate coated steel sheets are fed in a heat chamber (7) for drying at a temperature of 40°-60°C. After drying the sheets are coiled (8). As shown in figure.2-Bare rolled steel sheet (2) is passed through a first tension leveler (3,4) and then immerse in bath (9) containing poly phosphate coating solution. After coating adherence, the rolled steel sheet is passed again through a second tension leveier (3,4) for uniform lamination of coated material. The rolled steel sheet are further passed through two rubber squeezers (5,6) for better adherence of coating material. The poly phosphate coated rolled steel

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sheets are then fed to a chamber (7) for drying at a temperature of 40°-60°C. The dried sheets are coiled in a machine (8).

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WE CLAIM
1. A method for poly phosphate coating on Rolled steel sheet to resist corrosion in poly-season climatic atmosphere comprising
- a poly phosphate coating solution are sprayed from a spray gun (1) on a moving bare rolled sheets (2) and the swabbed sheets are passed through two taveller (3, 4) for uniform coating and the excess solution fall on a bath (9) placed beneath the spray gun (1) and the moving sheets coated with poly-phosphate are further squeezed by means of two rubber rollers (5, 6) and there after the laminated poly-phosphate coated sheets are fed in a heat chamber (7) for drying at a temperature of 40°- 60°C and after drying the sheets are coiled (8)
2. A method for poly phosphate coating on Rolled steel sheet to resist corrosion in poly-season climatic atmosphere comprising

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- a bare roiled steel sheet (2) is passed through a first tension leveler (3,4) then immersed in bath (9) containing poly-phosphate coating solution and having coating adherence, the roller sheet is again passed through a second tension leveler (3,4) for uniform lamination and further squeezed by two rubber squeezers (5,6) for better adherence of coating material and the coated sheets are fed to a chamber (7) for drying at a temperature of 40°-60°C and coiled In machine (8).
3. A method for poly-phosphate coating on Rolled Steel Sheet to resist corrosion in poly-season climatic atmosphere as substantially described and illustrated herein with reference to the accompanying drawing.

Documents:

01073-kol-2006 abstract.pdf

01073-kol-2006 claims.pdf

01073-kol-2006 correspondence others.pdf

01073-kol-2006 description(complete).pdf

01073-kol-2006 drawings.pdf

01073-kol-2006 form-1.pdf

01073-kol-2006 form-2.pdf

01073-kol-2006 form-3.pdf

01073-kol-2006 gpa.pdf

01073-kol-2006-correspondence-1.1.pdf

01073-kol-2006-form-9.pdf

1073-KOL-2006-ABSTRACT.pdf

1073-KOL-2006-CLAIMS.pdf

1073-KOL-2006-CORRESPONDENCE-1.1.pdf

1073-KOL-2006-DESCRIPTION COMPLETE.pdf

1073-KOL-2006-DRAWINGS.pdf

1073-KOL-2006-FORM 1-1.1.pdf

1073-KOL-2006-FORM 1.pdf

1073-KOL-2006-FORM 2.pdf

1073-kol-2006-granted-abstract.pdf

1073-kol-2006-granted-claims.pdf

1073-kol-2006-granted-correspondence.pdf

1073-kol-2006-granted-description (complete).pdf

1073-kol-2006-granted-drawings.pdf

1073-kol-2006-granted-examination report.pdf

1073-kol-2006-granted-form 1.pdf

1073-kol-2006-granted-form 18.pdf

1073-kol-2006-granted-form 2.pdf

1073-kol-2006-granted-form 3.pdf

1073-kol-2006-granted-gpa.pdf

1073-kol-2006-granted-reply to examination report.pdf

1073-kol-2006-granted-specification.pdf

1073-KOL-2006-PITITION UNDER RULE 137.pdf

1073-KOL-2006-REPLY TO EXAMINATION REPORT.pdf

abstract-01073-kol-2006.jpg


Patent Number 235627
Indian Patent Application Number 1073/KOL/2006
PG Journal Number 30/2009
Publication Date 24-Jul-2009
Grant Date 09-Jul-2009
Date of Filing 16-Oct-2006
Name of Patentee TATA STEEL LIMITED
Applicant Address RESEARCH AND DEVELOPMENT AND SCIENTIFIC SERVICES DIVISION, JAMSHEDPUR
Inventors:
# Inventor's Name Inventor's Address
1 T. K. ROUT R&D & ROY RESEARCH & TECHNOLOGY TATA STEEL LIMITED, JAMSHEDPUR 831001
PCT International Classification Number N/A
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 NA