Title of Invention	A process for the preparation of novel flux useful for hot dip galvanizing of iron and iron based alloys and an improved process therefor using the said flux
Abstract	An improved process for the preparation of a novel flux useful for hot dip galvanizing of iron and iron based alloys which comprises: (i) Preparing 5 - 50% aqueous solution of zinc chloride and heating to a temperature in the range of 80 to 115°C. (ii) Preparing 10 - 50% aqueous solution of ammonium chloride and heating to a temperature in the range of 80 to 115°C, (iii) Mixing the solutions resulting from step (i) and (ii) above under constant stirring while maintaining the temperature under constant stirring while maintaining the temperature in the range of 70 to 110°C for a period of 30 to 150 minutes, (iv) evaporating the solution obtained in step (iii) to raise gravity and effect solidification of the reacted product, cooling the solution to room temperature for separating resultant flux from the unreacted salts

Title of Invention

A process for the preparation of novel flux useful for hot dip galvanizing of iron and iron based alloys and an improved process therefor using the said flux

Abstract

An improved process for the preparation of a novel flux useful for hot dip galvanizing of iron and iron based alloys which comprises: (i) Preparing 5 - 50% aqueous solution of zinc chloride and heating to a temperature in the range of 80 to 115°C. (ii) Preparing 10 - 50% aqueous solution of ammonium chloride and heating to a temperature in the range of 80 to 115°C, (iii) Mixing the solutions resulting from step (i) and (ii) above under constant stirring while maintaining the temperature under constant stirring while maintaining the temperature in the range of 70 to 110°C for a period of 30 to 150 minutes, (iv) evaporating the solution obtained in step (iii) to raise gravity and effect solidification of the reacted product, cooling the solution to room temperature for separating resultant flux from the unreacted salts

Full Text	This invention relates to a process for the preparation of a novel flux useful for hot dip galvanizing of iron and iron based alloys and an improved process therefor using the said flux. Iron and iron based alloys are hot dip galvanized in molten zinc to provide zinc coating on their surface. Since zinc is anodic to iron and steel, it provides sacrificial protection towards the surface of the latter. For hot dip galvanizing of different type of articles of iron and steels, the following steps are involved: (i) Pickling, (ii) Rinsing, (iii) Fluxing, (iv) Drying and (v) Hot dip galvanizing The present invention describes the synthesis and use of the * novel flux-(triple salt flux) used in hot dip galvanizing process. The fluxing ofthe surface to be galvanized enables it to get rid of oxides of iron present on the surface. These oxides if present on the surface create problems such as black spots on galvanized materials, dross formation, etc. The fluxing is achieved in two ways: (a) Dry fluxing: Where the article to be galvanized is treated in the solution of flux prior to their immersion in the molten zinc bath and (b) Wet fluxing: Where the surface to be galvanized is fluxed insitu into the molten zinc bath itself. The hitherto known processes for the fluxing is the use of a mixture of zinc chloride and ammonium .chloride in dry fluxing and ammonium chloride in wet fluxing. These known processes are, however, associated with a number of drawbacks such as: ' ....;. (a) They are extremely corrosive towards the steel articles, (b) Dross formation is very high, (c) Pollution problems are encountered due to ' : the decomposition of ammonium chloride to form ammonia and hydrochloric acid fumes and . (d) Black spots appear due to improper fluxing ie.uncleahed oxide on the surface. The main object of the present invention is to provide a process for the preparation of a novel flux useful for hot dip galvanizing o*f iron and iron based alloys. Another object is to provide an improved process for hot dip •galvanising using the said flux which obviates the above men tioned drawbacks. In the process of the present invention, a thin coating of iron-zinc-ammonium chloride is formed on the articles to be galvanized when they are dipped in the appropriate concen tration of novel flux consisting of triple salt dissolved in the water. : The triple salt is prepared by reaction of zinc chloride and ammonium chloride in an appropriate molecular ratio, tempera--ture and time. The triple salt is crystallized, filtered and used as flux at an appropriate concentration. Accordingly, the present invention provides an improved process for the preparation of a novel flux useful for hot dip galvanizing of iron and iron based alloys which comprises: (i) Preparing 5 - 50% aqueous solution of zinc chloride and heating to a temperature in the range of 80 to 115°C. (ii) Preparing 10 - 50% aqueous solution of ammonium chloride and heating to a temperature in the range of 80 to 115°C, (iii) Mixing the solutions resulting from step (i) and (ii) above under constant stirring while maintaining the temperature under constant stirring while maintaining the temperature in the range of 70 to 110°C for a period of 30 to 150 minutes, (iv) evaporating the solution obtained in step (iii) to raise gravity and effect solidification of the reacted product, cooling the solution to room temperature for separating resultant flux from the unreacted salts. According to a feature of invention the chloride of zinc and ammonia may be either laboratory reagent grade or commercial grade, but free from impurities such as iron. Accordingly, the present invention also provides an improved process for hot dip galvanizing using the said novel flux which comprises: (i) Preparing a bath of 15 to 20% aqueous solution of the novel flux prepared by the process as described above raising the temperature of the flux solutions in the temperature range o of 40 to 110 C, (ii) Dipping the metal substrate to be galvanized in the said bath for a period- in the range of of 30 to 300 seconds, (iii) Drying the fluxed metal substrate with hot air and (iv) Galvanizing the articles in molten zinc bath by known methods. By the process of the present invention , galvanizing of iron and iron based alloys is achieved having reduced iron based alloy dross generation( lOto 50%),galvanized coating of high adherence and least pollution to the atmosphere. The 'following examples are given by way of illustration and should not be construed to limit the scope of investigation: Example 1 A solution of zinc chloride containing 200 gms/lit of zinc chloride was prepared and heated to 100 C. Another solution of ammoniumchloride having 800 gms/lit was prepared and also heated to 100 C. Both these solutions were mixed in hot conditions under constant stirring. The mixed solution was boiled for 15 minutes and cooled to room temperature. The filtrate was taken and its specific gravity was raised to get the crystals of triple salt. The crystals were analyzed by X-ray diffractometryand the chemical methods.The strong peaks of ZnCl.3 NH Cl were observed in X-ray diffraction pattern. The chemical analysis exhibited the following results. % Zn 22.80 % Cl 60.06 %ZnC12 46.00 % NH4C1 54.00 Example 2 A solution having 300 gms/lit of zinc chloride and 600gms/lit of ammonium chloride was prepared and heated to 110 c.Thistemperature was maintained for 35 minutes. The solution was cooled to roomtemperature and filtrate was evaporated to raise its specific gravity and then cooled to achieve the crystals of Triple-salts.The crystals were analyzed using X-ray diffraction and chemical methods and results were the same as described in example 1. f Example 3 A water solution of 20% of the product prepared as in Examplel was prepared and small mild steel tube coupons (2.5 cm dia,1.0 mm thickness and 15.0 cm length) were treated in this solution for one minute at 80 to 90 C.These coupons were dried and immersed in the bath having molten zinc at 450 C. Following observations were noted: i) Evolution of white fumes was 50 to 70% less compared to the conventional process; ii Adherence of the coating evaluated by bend test passed the stipulated standard. (iii) Copper sulphate dip test: passes 12 dips. Example 4 A water solution having 40 gms/100 ml of the triple salt as prepared in Example II was heated to 100 C and tube specimen of dimensions(2.5 cm dia 1.0 mm thickness and 15.0 cm length) were treated in this solution for 1 minute. They were then dried and dipped in galvanizing bath maintained at 450 C. The following observations were noted: (i) The white fumes evolution was less by 50-70% compared to conventional bath; (ii) Adherence ofthe coating passed the standard tests of adherence . (iii) Copper sulphate dip test: Passed 12 dips. Corrosion Studies: i Mild steel coupons of size 7.5 cm x 7.5 cm were immersed in the solution prepared by this invention and also in the solution conventionally prepared,for 6 hours maintaining the temperature of the bath to 70 C. Following results were obtained: FLux Corrosion Rate (mpy) Triple salt based flux42 as prepared by the present invention Conventional flux 81 These figures indicate that the novel flux based on triple salt are less corrosive. The main advantages of the present invention are: (i) The present invention reduces the pollution problems compared to conventional fluxes by 50-70%. (ii) It is 50% less corrosive than the conventional fluxes. This is expected to reduce dross formation; (iii) Coating is very adherent to the steel surface; (iv) It can be operated at 30 to 40% lower concentrations compared to the conventional fluxes, in the bath leading to saving in space for storage of the chemicals and reduced hazard-ness due to the handling of diluted solution. We Claim: 1. An improved process for the preparation of a novel flux useful for hot dip galvanizing of iron and iron based alloys which comprises: (i) Preparing 5 - 50% aqueous solution of zinc chloride and heating to a temperature in the range of 80 to 115°C. (ii) Preparing 10 - 50% aqueous solution of ammonium chloride and heating to a temperature in the range of 80 to 115°C, (iii) Mixing the solutions resulting from step (i) and (ii) above under constant stirring while maintaining the temperature under constant stirring while maintaining the temperature in the range of 70 to 110°C for a period of 30 to 150 minutes, (iv) evaporating the solution obtained in step (iii) to raise gravity and effect solidification of the reacted product, cooling the solution to room temperature for separating resultant flux from the unreacted salts. 2. A process for the preparation of novel flux useful for hot dip galvanizing of iron and iron based alloys substantially as herein described with reference to the examples.

Full Text

This invention relates to a process for the preparation of a novel flux useful for hot dip galvanizing of iron and iron based alloys and an improved process therefor using the said flux.
Iron and iron based alloys are hot dip galvanized in molten zinc to provide zinc coating on their surface. Since zinc is anodic to iron and steel, it provides sacrificial protection towards the surface of the latter. For hot dip galvanizing of different type of articles of iron and steels, the following steps are involved:
(i) Pickling,
(ii) Rinsing,
(iii) Fluxing,
(iv) Drying and
(v) Hot dip galvanizing
The present invention describes the synthesis and use of the * novel flux-(triple salt flux) used in hot dip galvanizing process. The fluxing ofthe surface to be galvanized enables it to get rid of oxides of iron present on the surface. These oxides if present on the surface create problems such as black spots on galvanized materials, dross formation, etc.
The fluxing is achieved in two ways:
(a) Dry fluxing: Where the article to be galvanized is
treated in the solution of flux prior to their immersion in
the molten zinc bath and
(b) Wet fluxing: Where the surface to be galvanized is fluxed
insitu into the molten zinc bath itself.
The hitherto known processes for the fluxing is the

use of a mixture of zinc chloride and ammonium .chloride in dry
fluxing and ammonium chloride in wet fluxing. These known
processes are, however, associated with a number of drawbacks
such as: ' ....;.
(a) They are extremely corrosive towards the steel articles,
(b) Dross formation is very high,

(c) Pollution problems are encountered due to ' : the
decomposition of ammonium chloride to form ammonia and
hydrochloric acid fumes and .
(d) Black spots appear due to improper fluxing ie.uncleahed
oxide on the surface.
The main object of the present invention is to provide a process for the preparation of a novel flux useful for hot dip galvanizing o*f iron and iron based alloys.
Another object is to provide an improved process for hot dip
•galvanising using the said flux which obviates the above men
tioned drawbacks.
In the process of the present invention, a thin coating of
iron-zinc-ammonium chloride is formed on the articles to
be galvanized when they are dipped in the appropriate concen
tration of novel flux consisting of triple salt dissolved in
the water. :
The triple salt is prepared by reaction of zinc chloride and ammonium chloride in an appropriate molecular ratio, tempera--ture and time. The triple salt is crystallized, filtered and used as flux at an appropriate concentration.

Accordingly, the present invention provides an improved process for the preparation of a novel flux useful for hot dip galvanizing of iron and iron based alloys which comprises:
(i) Preparing 5 - 50% aqueous solution of zinc chloride and heating to a
temperature in the range of 80 to 115°C. (ii) Preparing 10 - 50% aqueous solution of ammonium chloride and
heating to a temperature in the range of 80 to 115°C, (iii) Mixing the solutions resulting from step (i) and (ii) above under
constant stirring while maintaining the temperature under constant
stirring while maintaining the temperature in the range of 70 to 110°C
for a period of 30 to 150 minutes, (iv) evaporating the solution obtained in step (iii) to raise gravity and effect
solidification of the reacted product, cooling the solution to room
temperature for separating resultant flux from the unreacted salts. According to a feature of invention the chloride of zinc and ammonia may be either laboratory reagent grade or commercial grade, but free from impurities such as iron.
Accordingly, the present invention also provides an improved process for hot dip galvanizing using the said novel flux which comprises: (i) Preparing a bath of 15 to 20% aqueous solution of the novel flux prepared by the process as described above raising the

temperature of the flux solutions in the temperature range
o of 40 to 110 C,
(ii) Dipping the metal substrate to be galvanized in the said bath for a period- in the range of of 30 to 300 seconds,
(iii) Drying the fluxed metal substrate with hot air and
(iv) Galvanizing the articles in molten zinc bath by known methods.
By the process of the present invention , galvanizing of iron
and
iron based alloys is achieved having reduced iron
based alloy dross generation( lOto 50%),galvanized coating
of high adherence and least pollution to the atmosphere.
The 'following examples are given by way of illustration and should not be construed to limit the scope of investigation:
Example 1
A solution of zinc chloride containing 200 gms/lit of zinc chloride was prepared and heated to 100 C. Another solution of ammoniumchloride having 800 gms/lit was prepared and also heated to 100 C. Both these solutions were mixed in hot conditions under constant stirring. The mixed solution was boiled for 15 minutes and cooled to room temperature.
The filtrate was taken and its specific gravity was raised to get the crystals of triple salt. The crystals were analyzed by X-ray diffractometryand the chemical methods.The strong peaks of ZnCl.3 NH Cl were observed in X-ray diffraction pattern. The

chemical analysis exhibited the following results.
% Zn 22.80
% Cl 60.06
%ZnC12 46.00
% NH4C1 54.00
Example 2
A solution having 300 gms/lit of zinc chloride and 600gms/lit of ammonium chloride was prepared and heated to 110 c.Thistemperature was maintained for 35 minutes. The solution was cooled to roomtemperature and filtrate was evaporated to raise its specific gravity and then cooled to achieve the crystals of Triple-salts.The crystals were analyzed using X-ray diffraction and chemical methods and results were the same as
described in example 1. f
Example 3
A water solution of 20% of the product prepared as in Examplel was prepared and small mild steel tube coupons (2.5 cm dia,1.0 mm thickness and 15.0 cm length) were treated in this solution for one minute at 80 to 90 C.These coupons were dried and immersed in the bath having molten zinc at 450 C. Following observations were noted:
i) Evolution of white fumes was 50 to 70% less compared to the conventional process;
ii Adherence of the coating evaluated by bend test passed the stipulated standard.

(iii) Copper sulphate dip test: passes 12 dips.
Example 4
A water solution having 40 gms/100 ml of the triple salt as prepared in Example II was heated to 100 C and tube specimen of dimensions(2.5 cm dia 1.0 mm thickness and 15.0 cm length) were treated in this solution for 1 minute. They were then dried and dipped in galvanizing bath maintained at 450 C. The following observations were noted:
(i) The white fumes evolution was less by 50-70% compared to conventional bath;
(ii) Adherence ofthe coating passed the standard tests of adherence .
(iii) Copper sulphate dip test: Passed 12 dips. Corrosion Studies:
i Mild steel coupons of size 7.5 cm x 7.5 cm were immersed in the
solution prepared by this invention and also in the solution conventionally prepared,for 6 hours maintaining the temperature of the bath to 70 C. Following results were obtained:
FLux Corrosion Rate
(mpy)
Triple salt based flux42
as prepared by the present
invention
Conventional flux 81
These figures indicate that the novel flux based on triple salt are less corrosive.

The main advantages of the present invention are:
(i) The present invention reduces the pollution problems compared to conventional fluxes by 50-70%.
(ii) It is 50% less corrosive than the conventional
fluxes. This is expected to reduce dross formation;
(iii) Coating is very adherent to the steel surface;
(iv) It can be operated at 30 to 40% lower concentrations compared to the conventional fluxes, in the bath leading to saving in space for storage of the chemicals and reduced hazard-ness due to the handling of diluted solution.

We Claim:
1. An improved process for the preparation of a novel flux useful for hot dip
galvanizing of iron and iron based alloys which comprises:
(i) Preparing 5 - 50% aqueous solution of zinc chloride and heating to a
temperature in the range of 80 to 115°C. (ii) Preparing 10 - 50% aqueous solution of ammonium chloride and
heating to a temperature in the range of 80 to 115°C, (iii) Mixing the solutions resulting from step (i) and (ii) above under
constant stirring while maintaining the temperature under constant
stirring while maintaining the temperature in the range of 70 to 110°C
for a period of 30 to 150 minutes, (iv) evaporating the solution obtained in step (iii) to raise gravity and effect
solidification of the reacted product, cooling the solution to room
temperature for separating resultant flux from the unreacted salts.
2. A process for the preparation of novel flux useful for hot dip galvanizing of
iron and iron based alloys substantially as herein described with reference
to the examples.

Documents:

2444-del-1997-abstract.pdf

2444-del-1997-claims.pdf

2444-del-1997-complete specification (granted).pdf

2444-del-1997-correspondence-others.pdf

2444-del-1997-correspondence-po.pdf

2444-del-1997-description (complete).pdf

2444-del-1997-form-1.pdf

2444-del-1997-form-19.pdf

2444-del-1997-form-2.pdf

2444-del-1997-form-3.pdf

2444-del-1997-petition-138.pdf

« Previous Patent

Next Patent »

Patent Number

228261

Indian Patent Application Number

2444/DEL/1997

PG Journal Number

38/2008

Publication Date

19-Sep-2008

Grant Date

29-Dec-2006

Date of Filing

28-Aug-1997

Name of Patentee

Council of Scientific and Industrial Research,

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	Davendra Deo Narayan Singh	National Metallurgical Laboratory, Jamshedpur, Bihar,INDIA.
2	Tej Bahadur Singh	National Metallurgical Laboratory, Jamshedpur, Bihar,INDIA.
3	Arun Kumar Dey	National Metallurgical Laboratory, Jamshedpur, Bihar,INDIA.

PCT International Classification Number

B05D 1/18

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA