1. A process for manufacturing of corrosion resistant Galvanized Steel Pipes made of special steel having low carbon and low Sulphur /Phosphorous , wherein , after chromate compounding of the pipes, the pipes are subjected to a coating of Polyurethane in following chronological stepsc) coating of high grade Zinc d) Coating of chromate e) Polyurethane coating.

2. A process for manufacturing of corrosion resistant Galvanized Steel Pipes as claimed in claim 1. wherein the thickness of the Polyurethane coating is in the range of 10 to 15 micron.

3. A process for manufacturing of corrosion resistant Galvanized Steel Pipes as claimed in claim 1, wherein chemical coating followed after chromate compounding is of Polyurethane, Acrylic or other organic coating.

4. Galvanized Steel Pipes coated with chromate compounding followed by Polyurethane, Acrylic or other organic coating manufactured by the process as claimed in claim 1.

INTRODUCTION,
This invention relates to a process for manufacturing corrosion resistant Galvanized
Steel Pipes which offers significant resistance to the effects of acidic, alkali and
environmental factors of corrosion surrounding the pipes. The invention is also
directed towards Galvanized Steel Pipes manufactured by the process mentioned
above.
BACKGROUND OF INVENTION
Galvanized Steel Pipes are extensively used for fluid supply including drinking
water transportation ,sanitary applications ,gas transportation conduit pipes etc. The
process of Galvanization i.e. Zinc Coating offers superior rust protection on Steel.
Steel pipes are prone to corrosion due to environment conditions. Pipes in the open
are exposed to rain, air , sun and other substances. Combination of water, air,
sunlight and other chemicals can corrode steel. Galvanized Pipes have also been
found to get corroded in the course of time more particularly prone when
galvanized steel pipes are concealed or buried which occur due to the material used in
construction.
To protect steel from corrosion, these pipes are galvanized. In the galvanization
process a layer of Zinc is coated on steel surface. An Iron-Zinc alloy is formed
over which further Zinc is added. This Zinc protects steel from corrosion.
Zinc is a corrosion-inhibitor for steel pipes and other steel articles. Pipes
galvanized with Zinc are known to be in service for long periods of times,
sometimes up to 50 years to 100 years. Earlier these pipes were commonly laid in
the open when there was only atmospheric condition effecting the pipes. With
modernization and increased attention to aesthetics, there is an increasing trend
towards burying these pipes under ground, walls or roofs.
When these pipes are buried, they came under the influence of different
chemicals present in their natural form or used in the construction industries.
These chemicals have an adverse impact on the Zinc coated on the pipes. It is
observed that the Zinc gets seriously corroded in the presence of Acidic or Alkaline
environment present in the construction materials. This reduces the life of
Galvanized Pipes significantly. The Zinc layer gets corroded and gets removed from
the pipes thus exposing the steel underneath. This steel is affected by moisture
present in the environment. The corroded steel gets pitted & develops hole. As a
result, users have become wary of using Galvanized Pipes in concealed or buried
applications.
OBJECT OF THE INVENTION:
The object of the invention is to provide a process for producing Galvanized Steel
Pipes with superior rust protection .
Another object of the invention is to provide a process for producing Galvanized
Steel Pipes which offers more resistant to atmospheric factors of corrosion.
Yet another object of the invention is to provide process for producing Galvanized
Steel Pipes which can resist the effects of acidic, alkali and environmental
factors surrounding the pipes.
Further object of the invention is directed towards a process of providing a
special coating of Polyurethane .acrylic or other organic compound during the
production of Galvanized Steel Pipes to increase durability of the pipes.
STATEMENT OF THE INVENTION
The invention provides a process for manufacturing of corrosion resistant
Galvanized Steel Pipes made of special steel having low carbon and low Sulphur
/Phosphorous , wherein , after chromate compounding of the pipes, the pipes are
subjected to a coating of Polyurethane in following chronological stepsa)
coating of high grade Zinc
b) Coating of chromate
c) Polyurethane coating
According to the new invention, the Galvanized Steel Pipes are coated with chromate
compounding followed by chemical coating including Polyurethane, Acrylic or other
organic coating.
The thickness of the Polyurethane coating is in the range of 10 to 15 micron.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING:
The foregoing aspects and many of the advantages of this invention will become more
readily appreciated by following detailed description when taken in conjunction with
the accompanying drawing, wherein.
Fig 1. Shows the details of machinery involved in the manufacturing process of the
Galvanized Steel Pipes in accordance with the present invention.
DETAILED DESCRIPTION OF THE MANUFACTURING PROCESS IN
REFERENCE TO DRAWING :
In reference to the accompanying drawing fig.l the detail manufacturing process is
described below-
Pipes are manufactured out of special type of steel with low carbon and low Sulphur
/Phosphorous. This increases corrosion-resistance of steel. Further special corrosion
steels using Copper or Nickel or Chromium in isolation or combination are also used
for manufacturing these steel pipes. During production, a special coolant containing
anti-corrosive chemical is used. This prevents or delays oxidation/corrosion during
processing. The pipes are quickly galvanized in a hot dip galvanized bath using
special high grade zinc.
The Galvanized pipes are passed through a chemical process for chromate coating.
Pipes are put in a chromate tank for a specified period.
The Galvanized pipe with Zinc coating is kept on frame for Acrylic-coating in
bundles. There are conveyors on which rolls of galvanized steel pipes are placed.
These Galvanized pipes are fed to the conveyor for the process. All the conveyors
rolls are attached with belt arrangement with a motor drive. With a single motor
all conveyors are rolled together which helps the pipe to move straight. Power rolls
tends to align in the one direction to the pipe.
There is a system for spray of acrylic on the outer surface of pipe. The acrylic
solution is poured in a tank which is fabricator of Mild Steel. Acrylic solution is
collected in the mild steel Tank. With the help of a pump this acrylic solution is
sprayed on the pump which is sprayed with the help of a nozzle. When this acrylic
solution is sprayed on the outer surface of the galvanized steel pipe a layer of acrylic
solution is formed on it. With the help of a wiper which wipe out excess solution
from the pipe and it collect the solution in the tank and extra solution is again fed
into the solution tank by a reverse pipe. A layer of 10-15 microns is required to
deposit on pipe. There is air dies which again control the protective layer on pipe.
Air is controlled by Air valves which is present in circuit. Compressed air is
required for the system. Compressed air is supplied through a compressor which is
installed near in Galvanizing section.
After passing through air dies these pipes are fed through a hot air chamber. The hot
air temperature in range from 40°C-90°C depending upon the ambient temperature.
The hot air is required to dry up the pipe coating as soon as possible, which need to
be dried soon so that the coating does not split off and when this coating is formed
on pipe it cannot stuck off by any media .
There is a temperature bath in the system, where a healer placed in the chamber with
thermostat to control temperature. The air is passed through a coil in this chamber.
Air is exposed to heat to get the desired temperature in the range of 40CC - 90°C
which is controllable with the help of a thermostat installed in chamber. Thermostat
cut the power supply of the heater at what temperature it is settled and again when
the temperature goes below it again on the supply to heater.
The hot air is sprayed on the pipes which are passed through a chamber to dry up
the pipes as early as possible. In the chamber hot air is sprayed in open to maintain
the temperature in the chamber.
After passing through hot air chamber there is an open air cooling zone for the
pipes. After drying pipes in hot air chamber these pipes are dried in open air
cooling zone to protect coating layer.
After drying up of the protective layer coated pipes, these pipes are collected in a
pipe collection pocket and stored in a place.
INDUSTRIAL APPLICABILITY:
Galvanized Steel Pipes manufactured by the process of present invention offers
more resistance to the effects of acidic, alkali and environmental factors surrounding
the pipes.
The major advantage of these pipes is increase in the durability and life span of
these pipes thereby reducing the cost associated with frequent replacement of rusted
pipes.

We Claim:
1. A process for manufacturing of corrosion resistant Galvanized Steel Pipes made
of special steel having low carbon and low Sulphur /Phosphorous , wherein , after
chromate compounding of the pipes, the pipes are subjected to a coating of
Polyurethane in following chronological stepsc)
coating of high grade Zinc
d) Coating of chromate
e) Polyurethane coating.
2. A process for manufacturing of corrosion resistant Galvanized Steel Pipes as
claimed in claim 1. wherein the thickness of the Polyurethane coating is in the
range of 10 to 15 micron.
3. A process for manufacturing of corrosion resistant Galvanized Steel Pipes as
claimed in claim 1, wherein chemical coating followed after chromate
compounding is of Polyurethane, Acrylic or other organic coating.
4. Galvanized Steel Pipes coated with chromate compounding followed by
Polyurethane, Acrylic or other organic coating manufactured by the process as
claimed in claim 1.