Title of Invention	A METHOD FOR DEPOSITION OF ANTI-CORROSIVE COATING ON METALLIC AND NON-METALLIC SUBSTRATE SURFACE
Abstract	The present invention is provided with a method for depositing an anti-corrosive coating on metallic and non-metallic substrate surfaces, comprising treating the substrate with a sensitizer solution to obtain the sensitized substrate, followed by treating the sensitized substrate to activation by treating with an activator solution, dipping the activated substrate into an electroless coating bath comprising a plating solution of a nickel compound, a complexing agent and a stabilizer, allowing deposition to continue for 7 to 10 min and annealing the coated substrate.

Title of Invention

A METHOD FOR DEPOSITION OF ANTI-CORROSIVE COATING ON METALLIC AND NON-METALLIC SUBSTRATE SURFACE

Abstract

The present invention is provided with a method for depositing an anti-corrosive coating on metallic and non-metallic substrate surfaces, comprising treating the substrate with a sensitizer solution to obtain the sensitized substrate, followed by treating the sensitized substrate to activation by treating with an activator solution, dipping the activated substrate into an electroless coating bath comprising a plating solution of a nickel compound, a complexing agent and a stabilizer, allowing deposition to continue for 7 to 10 min and annealing the coated substrate.

Full Text	FIELD OF THE INVENTION: This invention relates to a method for despositing anti-corrosive coating on metallic and non-metallic substrate surfaces. This invention further relates to a method for depositing Ni based pore free anti-corrosive coating of Group VA metals on metallic and non-metallic surfaces, by ion-exchange auto catalytic process. The deposit is hard enough to withstand salty, acidic, alkaline and corrosive gaseous environment. The coating provided has utilization in various industries like, Motor industries, aerospace industries, Chemical industries, Electronics industries, Food processing industries and Textile industries. BACKGROUND OF THE INVENTION: Oil and gas are explored from remote rural and unmanned areas. The metallic items like valves, exhaust stacks, pipe castings and conveyor components are used in oil and gas lifting as well as transporting them to the refineries. These items are made of metals and non-metals and are of complex shapes and sizes. They are mainly made of steel with various percentage of carbon that are affected in salty and acidic environment. The oil and gas environment is composed of corrosive gases like CO2, H2S. Dissolving these gases in water from an acidic environment and corrode the above items. As a result the lifetime of the above items are limited in the oil and gaseous atmosphere. The items mentioned above are placed at very remote locations like in the bed of sea, in desert etc. Damage, due to corrosion causes not only a big loss in terms of spillage of oil and gas and consequently financial loss but also renders the components vulnerable to environment. The difficulties of protecting substrate surface from corrosion particularly in oil and gas environment are known in the art. Therefore, the need exists, to protect the components to ensure proper functioning on a long term basis. OBJECTS OF THE INVENTION: It is therefore an object of this invention to propose a method for depositing an anti-corrosive coating on metallic and non-metallic surfaces, which is simple and cost effective. It is a further object of this invention to propose a method for depositing an anti- corrosive coating on metallic and non-metallic surfaces, which employs easily available raw materials and apparatus. These and other objects of the invention will be apparent from the ensuing description. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS: This invention will be explained in greater detail with the help of the accompanying drawings where 1. Figure 1 is the diagram for testing the coating in salty environment. 2. Figure 2 is the corrosion characteristics of coating in salty environment. 3. Figure 3 is the diagram for testing coating in corrosive gas environment. 4. Figure 4 is the corrosion characteristics of coating in gaseous environment. 5. Figure 5 shows the photographs of some coated samples. DESCRIPTION OF THE INVENTION: Thus according to this invention is provided a method for depositing an anti- corrosive coating on metallic and non-metallic surfaces. According to this invention further provided a solution composition for deposition of NixPy coating at various x and y values. Ni - stands for Nickel P - stands for Phosphorous x and y are the percentage of metal and non-metal embedded in the coating. In accordance with this invention, the coating is deposited from solution by an ion-exchange auto-catalytic process, without the passage of electricity. In general, the method involves the preparation of a chemical solution for electroless bath and surface treatment of metallic substrates like mild steel, cast iron etc. for deposition of NixPy. For deposition of NixPy using electroless technique a special type of solution bath is prepared. The solution consists of salts of Ni like NiCl2, NiSO4 or NiCO3 or combinations thereof, a reducing agent like Na2HPO2, a complexing agent such as sodium succinate and a stabilizer such as lead acetate Nickel chloride is used in a proportion of 60 to 220 gms per litre, nickel sulphate in 60 to 200 gms/litre and nickel carbonate in 50 to 190 gms per litre of water. The reducing agent sodium hypophosphite is present in 5.5 to 35.5 gms/litre. The complexing agent and stabilizing agents are present in trace quantities of about 100 mg/litre of water. The above chemicals are mixed in particular proportion to have the exact solution strength. The solution is then warmed up to a temperature of 90-95°C. Metallic items of the above categories are treated in two other solutions. These are sensitizer and activator. The sensitizer solution is a mixture a tin salt such as for e.g. SnCl2 and an acid such as for example HCI. Tin chloride is present in 5 to 15 gms per litre of water and hydrochloric acid in 5 to 15 ml/litre of water. On the other hand the activator solution is a mixture of salt like PdCI2 and an acid with HCI. Palladium chloride is used in 300 to 500 mg/litre of water and hydrochloric acid in 5 to 15 ml/litre of water. Before deposition of NixPy layer the substrate surface is treated with sensitizer and activator solutions. The substrate is then put in the plating solution for the deposition of NixPy layer. Multi -layered coating are provided to make it pore free. Total thickness of the coating can range upto 20 µrn. The substrates are cleaned in cleaning solution to remove contaminations like grease and rust. The substrates are then treated in sensitizer solution to sensitize the substrate surface. After sensitization the substrate is activated in activator solution. After activation the substrates dipped in plating bath to deposit NixPy coating. Deposition was allowed for 7-10 mins. to have good coating. The substrates are then annealed in air at a temperature more than 250°C. The annealing enhances the contacting performance. According to the present method solution preparation is different from commercial solutions due to the incorporation of chemical at various percentage. The plating is conducted at a particular optimized condition and as a result exact percentage of P can be incorporated. The percentage of phosphorus control the corrosion resistance. The above coating was deposited from the ion exchanged autocatalytic process for the solution. As no electricity is involved in this coating process it is termed as electroless plating technique. The coating developed using the above technique has the following characteristic features: • The reduction of metallic ions occur in presence of Hypophosphite at the substrate surface, chiefly belonging to the eighth group of periodic table, which are capable of catalyzing the process; • The rate of deposition is greatly influenced by the temperature of the solution and is governed by exponential law; • The rate of reduction of metallic ions is strongly influenced by the pH value of the solution; • The deposit obtained from such solution is not a pure metallic one but always contains come percentage of phosphorous, a component of the reductant, the amount of which depends on the operating conditions and particularly the pH level of the solution; • The deposition of metallic ions takes place with the evolution of hydrogen. Thus, the invention also provides a solution composition of solution for deposition of NixPy coating at various of x and y as desired for. The invention will now be explained in greater details with the help of the following non limiting examples. Example 1: An electrolysis bath is prepared by dissolving 200 gms nickel chloride 20.5 gms of sodium hypophosphite, in a litre of water and warming the solution to 92°C. A sensitizer solution is prepared by dissolving 10 g of tin chloride and 10 ml hydrochlorine acid in a litre of water and an activator solution is prepared by dissolving 400 mg palladium chloride and 10 ml hydrochloric acid in a litre of water. The substrate is treated with a standard cleaning solution to remove grease and rust and then treated with the sensitizer solution for sensitization, followed by the activator solution. The activated substrate is then dipped in the electrolysis bath and deposition is allowed for approximately 6 min for a good coating. The substrates are then annealed in air at above 250°C to obtain the coated substrates. Example 2 The same procedure as for Example 1 is followed using 183gms of nickel sulphate salt instead of nickel chloride in the electrolysis bath. Example 3 The same procedure as for Example 1 is followed using 165gms nickel carbonate salt. Example 4 The same procedure as for Example 1 is followed using a mixture of 100 gms nickel chloride and 92 gms Nickel sulphate in the electrolysis bath. Example 5 The same procedure as for Example 1 is followed using a mixture of 92 gms nickel sulphate and 83 gms nickel carbonate in the electrolysis bath. Example 6 The same procedure as for Example 1 is followed using a mixture of 100 gms nickel chloride and 83 gms nickel carbonate in the electrolysis bath. Example 7 The same procedure as for Example 1 is followed using a mixture of 67 gms nickel chloride, 61 gms nickel sulphate and 55 gms nickel carbonate in the electrolysis bath. The substrates coated according to the invention are tested for their properties and Figure 1 shows the set up and methodology employed for testing in salty environment. The corrosion characteristic in salty environment is presented in Figure 2. Figure 2 indicates that corrosion rate is very low and expected coating life is very high. In Figure 3 a testing arrangement for corrosion resistance of coating in gas environment is shown. The corrosion resistance characteristics in gaseous environment is depicted in Figure 4. WE CLAIM: 1. A method for depositing an anti-corrosive coating on metallic and non- metallic substrate surfaces, comprising treating the substrate with a sensitizer solution to obtain the sensitized substrate, followed by treating the sensitized substrate to activation by treating with an activator solution, dipping the activated substrate into an electroless coating bath comprising a plating solution of a nickel compound, a complexing agent and a stabilizer, allowing deposition to continue for 7 to 10 min and annealing the coated substrate. 2. The method as claimed in claim 1, wherein said sensitizer solution comprises a tin compound such as for eg tin chloride and hydrochloric acid. 3. The method as claimed in claim 1, 2, wherein the tin compound is present in 5 to 15 g/lt and hydrochloric acid in 5 to 15 ml/1 of the solution. 4. The method as claimed in claim 1, wherein the activator solution comprises a palladium salt such as for eg palladium chloride and hydrochloric acid. 5. The method as claimed in claim 1, wherein palladium chloride is present in 300 to 500 mg/ml and hydrochloric acid in 5 to 15 m/l of the solution. 6. The method as claimed in claim 1, wherein said nickel compound is selected from nickel chloride, nickel sulphate and nickel carbonate and combinations thereof. 7. The method as claimed in claim 7, wherein nickel chloride is present in 60 to 220 gms/l, nickel sulphate is present in 60 to 200 gms/l and nickel carbonate in 50 to 190 gms/l of the electroless solution. 8. The method as claimed in claim 1, wherein the reducing agent is such as sodium hypophosphite. 9. The method as claimed in claim 1, wherein sodium hypophosphite is present in 5.5 to 35.5 gms/l. 10. The method as claimed in claim 1, wherein the complexing agent is such as sodium succinate in trace quantity. 11. The method as claimed in claim 1, wherein the stabilizer is such as lead acetate in trace quantity. 12. The method as claimed in claim 1, wherein the coated substrate is annealed at a temperature greater than 250°C. 13. A plating composition for electroless plating metallic and non-metallic substrates comprising a nickel compound selected from nickel chloride, nickel sulphate, nickel carbonate and combinations thereof, 5.5. to 35.5 gms/l of a reducing agent such as sodium hypophosphite in a complexing agent such as sodium succinate and a stabilizer such as lead acetate in trace quantities. 14. The plating composition as claimed in claim 13, wherein nickel chloride is present in 60 to 220 gms/l, nickel sulphate is present in 60 to 200 gms/l and nickel carbonate in 50 to 190 gms/l of the electroless solution. ABSTRACT A METHOD FOR DEPOSITION OF ANTI-CORROSIVE COATING ON METALLIC AND NON-METALLIC SUBSTRATE SURFACE The present invention is provided with a method for depositing an anti-corrosive coating on metallic and non-metallic substrate surfaces, comprising treating the substrate with a sensitizer solution to obtain the sensitized substrate, followed by treating the sensitized substrate to activation by treating with an activator solution, dipping the activated substrate into an electroless coating bath comprising a plating solution of a nickel compound, a complexing agent and a stabilizer, allowing deposition to continue for 7 to 10 min and annealing the coated substrate.

Full Text

FIELD OF THE INVENTION:
This invention relates to a method for despositing anti-corrosive coating on
metallic and non-metallic substrate surfaces. This invention further relates to a
method for depositing Ni based pore free anti-corrosive coating of Group VA
metals on metallic and non-metallic surfaces, by ion-exchange auto catalytic
process. The deposit is hard enough to withstand salty, acidic, alkaline and
corrosive gaseous environment. The coating provided has utilization in various
industries like, Motor industries, aerospace industries, Chemical industries,
Electronics industries, Food processing industries and Textile industries.
BACKGROUND OF THE INVENTION:
Oil and gas are explored from remote rural and unmanned areas. The metallic
items like valves, exhaust stacks, pipe castings and conveyor components are
used in oil and gas lifting as well as transporting them to the refineries. These
items are made of metals and non-metals and are of complex shapes and sizes.
They are mainly made of steel with various percentage of carbon that are
affected in salty and acidic environment. The oil and gas environment is
composed of corrosive gases like CO2, H2S. Dissolving these gases in water from
an acidic environment and corrode the above items. As a result the lifetime of
the above items are limited in the oil and gaseous atmosphere. The items
mentioned above are placed at very remote locations like in the bed of sea, in
desert etc. Damage, due to corrosion causes not only a big loss in terms of
spillage of oil and gas and consequently financial loss but also renders the
components vulnerable to environment.
The difficulties of protecting substrate surface from corrosion particularly in oil
and gas environment are known in the art. Therefore, the need exists, to protect
the components to ensure proper functioning on a long term basis.

OBJECTS OF THE INVENTION:
It is therefore an object of this invention to propose a method for depositing an
anti-corrosive coating on metallic and non-metallic surfaces, which is simple and
cost effective.
It is a further object of this invention to propose a method for depositing an anti-
corrosive coating on metallic and non-metallic surfaces, which employs easily
available raw materials and apparatus.
These and other objects of the invention will be apparent from the ensuing
description.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
This invention will be explained in greater detail with the help of the
accompanying drawings where
1. Figure 1 is the diagram for testing the coating in salty environment.
2. Figure 2 is the corrosion characteristics of coating in salty
environment.
3. Figure 3 is the diagram for testing coating in corrosive gas
environment.
4. Figure 4 is the corrosion characteristics of coating in gaseous
environment.
5. Figure 5 shows the photographs of some coated samples.
DESCRIPTION OF THE INVENTION:
Thus according to this invention is provided a method for depositing an anti-
corrosive coating on metallic and non-metallic surfaces.

According to this invention further provided a solution composition for deposition
of NixPy coating at various x and y values.
Ni - stands for Nickel
P - stands for Phosphorous
x and y are the percentage of metal and non-metal embedded in the coating.
In accordance with this invention, the coating is deposited from solution by an
ion-exchange auto-catalytic process, without the passage of electricity. In
general, the method involves the preparation of a chemical solution for
electroless bath and surface treatment of metallic substrates like mild steel, cast
iron etc. for deposition of NixPy. For deposition of NixPy using electroless
technique a special type of solution bath is prepared. The solution consists of
salts of Ni like NiCl2, NiSO4 or NiCO3 or combinations thereof, a reducing agent
like Na2HPO2, a complexing agent such as sodium succinate and a stabilizer such
as lead acetate Nickel chloride is used in a proportion of 60 to 220 gms per litre,
nickel sulphate in 60 to 200 gms/litre and nickel carbonate in 50 to 190 gms per
litre of water. The reducing agent sodium hypophosphite is present in 5.5 to 35.5
gms/litre. The complexing agent and stabilizing agents are present in trace
quantities of about 100 mg/litre of water. The above chemicals are mixed in
particular proportion to have the exact solution strength. The solution is then
warmed up to a temperature of 90-95°C. Metallic items of the above categories
are treated in two other solutions. These are sensitizer and activator. The
sensitizer solution is a mixture a tin salt such as for e.g. SnCl2 and an acid such
as for example HCI. Tin chloride is present in 5 to 15 gms per litre of water and
hydrochloric acid in 5 to 15 ml/litre of water. On the other hand the activator
solution is a mixture of salt like PdCI2 and an acid with HCI. Palladium chloride is

used in 300 to 500 mg/litre of water and hydrochloric acid in 5 to 15 ml/litre of
water. Before deposition of NixPy layer the substrate surface is treated with
sensitizer and activator solutions. The substrate is then put in the plating solution
for the deposition of NixPy layer. Multi -layered coating are provided to make it
pore free. Total thickness of the coating can range upto 20 µrn.
The substrates are cleaned in cleaning solution to remove contaminations like
grease and rust. The substrates are then treated in sensitizer solution to
sensitize the substrate surface. After sensitization the substrate is activated in
activator solution. After activation the substrates dipped in plating bath to
deposit NixPy coating. Deposition was allowed for 7-10 mins. to have good
coating.
The substrates are then annealed in air at a temperature more than 250°C. The
annealing enhances the contacting performance.
According to the present method solution preparation is different from
commercial solutions due to the incorporation of chemical at various percentage.
The plating is conducted at a particular optimized condition and as a result exact
percentage of P can be incorporated. The percentage of phosphorus control the
corrosion resistance.
The above coating was deposited from the ion exchanged autocatalytic process
for the solution. As no electricity is involved in this coating process it is termed as
electroless plating technique.
The coating developed using the above technique has the following characteristic
features:

• The reduction of metallic ions occur in presence of Hypophosphite at the
substrate surface, chiefly belonging to the eighth group of periodic table,
which are capable of catalyzing the process;
• The rate of deposition is greatly influenced by the temperature of the
solution and is governed by exponential law;
• The rate of reduction of metallic ions is strongly influenced by the pH
value of the solution;
• The deposit obtained from such solution is not a pure metallic one but
always contains come percentage of phosphorous, a component of the
reductant, the amount of which depends on the operating conditions and
particularly the pH level of the solution;
• The deposition of metallic ions takes place with the evolution of hydrogen.
Thus, the invention also provides a solution composition of solution for
deposition of NixPy coating at various of x and y as desired for.
The invention will now be explained in greater details with the help of the
following non limiting examples.
Example 1:
An electrolysis bath is prepared by dissolving 200 gms nickel chloride 20.5 gms
of sodium hypophosphite, in a litre of water and warming the solution to 92°C.
A sensitizer solution is prepared by dissolving 10 g of tin chloride and 10 ml
hydrochlorine acid in a litre of water and an activator solution is prepared by
dissolving 400 mg palladium chloride and 10 ml hydrochloric acid in a litre of
water.

The substrate is treated with a standard cleaning solution to remove grease and
rust and then treated with the sensitizer solution for sensitization, followed by
the activator solution. The activated substrate is then dipped in the electrolysis
bath and deposition is allowed for approximately 6 min for a good coating. The
substrates are then annealed in air at above 250°C to obtain the coated
substrates.
Example 2
The same procedure as for Example 1 is followed using 183gms of nickel
sulphate salt instead of nickel chloride in the electrolysis bath.
Example 3
The same procedure as for Example 1 is followed using 165gms nickel carbonate
salt.
Example 4
The same procedure as for Example 1 is followed using a mixture of 100 gms
nickel chloride and 92 gms Nickel sulphate in the electrolysis bath.
Example 5
The same procedure as for Example 1 is followed using a mixture of 92 gms
nickel sulphate and 83 gms nickel carbonate in the electrolysis bath.
Example 6

The same procedure as for Example 1 is followed using a mixture of 100 gms
nickel chloride and 83 gms nickel carbonate in the electrolysis bath.
Example 7
The same procedure as for Example 1 is followed using a mixture of 67 gms
nickel chloride, 61 gms nickel sulphate and 55 gms nickel carbonate in the
electrolysis bath.
The substrates coated according to the invention are tested for their properties
and Figure 1 shows the set up and methodology employed for testing in salty
environment. The corrosion characteristic in salty environment is presented in
Figure 2. Figure 2 indicates that corrosion rate is very low and expected coating
life is very high. In Figure 3 a testing arrangement for corrosion resistance of
coating in gas environment is shown. The corrosion resistance characteristics in
gaseous environment is depicted in Figure 4.

WE CLAIM:
1. A method for depositing an anti-corrosive coating on metallic and non-
metallic substrate surfaces, comprising
treating the substrate with a sensitizer solution to obtain the sensitized
substrate,
followed by treating the sensitized substrate to activation by treating with
an activator solution,
dipping the activated substrate into an electroless coating bath comprising
a plating solution of a nickel compound, a complexing agent and a
stabilizer,
allowing deposition to continue for 7 to 10 min and annealing the coated
substrate.
2. The method as claimed in claim 1, wherein said sensitizer solution
comprises a tin compound such as for eg tin chloride and hydrochloric
acid.
3. The method as claimed in claim 1, 2, wherein the tin compound is present
in 5 to 15 g/lt and hydrochloric acid in 5 to 15 ml/1 of the solution.
4. The method as claimed in claim 1, wherein the activator solution
comprises a palladium salt such as for eg palladium chloride and
hydrochloric acid.
5. The method as claimed in claim 1, wherein palladium chloride is present in
300 to 500 mg/ml and hydrochloric acid in 5 to 15 m/l of the solution.

6. The method as claimed in claim 1, wherein said nickel compound is
selected from nickel chloride, nickel sulphate and nickel carbonate and
combinations thereof.
7. The method as claimed in claim 7, wherein nickel chloride is present in
60 to 220 gms/l, nickel sulphate is present in 60 to 200 gms/l and
nickel carbonate in 50 to 190 gms/l of the electroless solution.
8. The method as claimed in claim 1, wherein the reducing agent is such
as sodium hypophosphite.
9. The method as claimed in claim 1, wherein sodium hypophosphite is
present in 5.5 to 35.5 gms/l.
10. The method as claimed in claim 1, wherein the complexing agent is
such as sodium succinate in trace quantity.
11. The method as claimed in claim 1, wherein the stabilizer is such as
lead acetate in trace quantity.
12. The method as claimed in claim 1, wherein the coated substrate is
annealed at a temperature greater than 250°C.
13. A plating composition for electroless plating metallic and non-metallic
substrates comprising a nickel compound selected from nickel chloride,
nickel sulphate, nickel carbonate and combinations thereof, 5.5. to
35.5 gms/l of a reducing agent such as sodium hypophosphite in a
complexing agent such as sodium succinate and a stabilizer such as
lead acetate in trace quantities.

14. The plating composition as claimed in claim 13, wherein nickel chloride
is present in 60 to 220 gms/l, nickel sulphate is present in 60 to 200
gms/l and nickel carbonate in 50 to 190 gms/l of the electroless
solution.

ABSTRACT

A METHOD FOR DEPOSITION OF ANTI-CORROSIVE COATING
ON METALLIC AND NON-METALLIC SUBSTRATE SURFACE
The present invention is provided with a method for depositing an anti-corrosive
coating on metallic and non-metallic substrate surfaces, comprising treating the
substrate with a sensitizer solution to obtain the sensitized substrate, followed by
treating the sensitized substrate to activation by treating with an activator
solution, dipping the activated substrate into an electroless coating bath
comprising a plating solution of a nickel compound, a complexing agent and a
stabilizer, allowing deposition to continue for 7 to 10 min and annealing the
coated substrate.

A METHOD FOR DEPOSITION OF ANTI-CORROSIVE COATING ON METALLIC AND NON-METALLIC SUBSTRATE SURFACE

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