Indian Patents. 253452:"CORROSION RESISTANT PHOSPHORIC IRON FOR CONCRETE EMBEDMENT AND REINFORCEMENT"

Title of Invention	"CORROSION RESISTANT PHOSPHORIC IRON FOR CONCRETE EMBEDMENT AND REINFORCEMENT"
Abstract	The present invention relates to a corrosion resistant phosphoric iron for concrete embedment and reinforcement comprising: Phosphorus: 0.110-0.490% Carbon: 0.020-0.028%, Silicon: 0.020-0.029% Manganese: 0.010 - 0.047 % Sulphur: 0.0 10 -0.018% Copper: 0.004 - 0.031 % all by weight and rest is iron.

Full Text	FIELD OF INVENTION: The present invention relates to the area of reinforcing steel/ embedment, which is corrosion resistant in concrete e.g. Buildings, Bridges and other civil works. PRIOR ART: Corrosion degradation of reinforcing steel/embedment in concrete is of great concern because it is the most widespread cause of degradation of reinforced concrete structures. The prevalent practice to overcome this problem of reinforcement corrosion is by using corrosion resistant steel bar, which is costly and contain copper, chromium, molybdenum and vanadium in small amount. Following are some inventions where costly elements are used to get corrosion resistant steel bar. JP3020441, discloses a salt-resistant reinforcing steel bar for preventing the deterioration of concrete contains 0.001 to 0.1% C, 0.01 to 0.05% Si, 0.01 to such as sea salt grains and sea water splashes penetrating into a concrete wall and the generation of cracks in concrete. JP5 8077552, discloses a salt resistant steel bar for reinforced concrete consists of, by weight, =l% kind of rare earth element and the balance Fe with inevitable impurities. The steel bar has superior resistance to corrosion due to salt in concrete. JP58077551, discloses a steel bar consists of, by weight JP61284552, discloses an iron reinforcing rod for reinforced concrete is made of a composition containing by weight, 0.001-1.0% C, JP62188754, discloses a reinforcing steel bar having superior corrosion resistance, is composed of, by weight, 0.01-0.4% C, 0.05-2% Si, 0.3-2% Mn, 0.3-5% Cr, 0.5-1.5% Cu, 0.001-0.05% Al, one or more among 0.01-1.5% Ni, 0.01-0.3% Mo and 0.01-0.3% V and the balance Fe with inevitable impurities. The composition may further contain 0.01-0.05% P. JP62199748, discloses reinforcing steel rod in a reinforced concrete structure installed at the seaside or in the sea is made of a steel having a composition containing by weight, JP2170945, discloses a reinforcing steel, to drastically delay its corrosion caused by salt in the free condition of Cl; the reinforcing steel bar containing by weight, 0.01 to 1.0% C, >0.05 to 0.18% Si, 0.01 to 0.3% Mn, or two kinds among Nb, V and Ti or furthermore, 0.01 to 0.3% Cu are added to the composition. JP3183740, discloses a composition of a reinforcing bar, which contains by weight 0.001 to 1.0% C, 0.01 to 0.05% Si, 0.01 to JP3020441: discloses a salt-resistant reinforcing bar for preventing the deterioration of concrete, which contains by weight 0.001 to 0.1% C, 0.01 to 0.05% Si, 0.01 to . STATEMENT OF INVENTION: The presence of costly elements as disclosed in the prior art, the reinforcing steel/embedment becomes costly. The reinforcing steel/embedment produced in the instant invention is cheaper and affordable. So, the present invention relates to a corrosion resistant phosphoric iron for concrete embedment and reinforcement comprising: Phosphorus : 0.110-0.490% Carbon : 0.020-0.028% Silicon : 0.020-0.029% Manganese : 0.010 - 0.047 % Sulphur : 0.010 - 0.018 % Copper : 0.004 - 0.031 % all by weight and rest is iron. Three corrosion resistant phosphoric iron samples were prepared to compare their efficacy with TATA TISCON and TATA CRS, which are readily available in the market. The constituents of these corrosion resistant phosphoric iron samples are: EXAMPLE 1 (P1) Phosphorus : 0.110% Carbon : 0.025 % Silicon : 0.028% Manganese : 0.046 % Sulphur : 0.017% Copper : 0.030 % all by weight and rest is iron. EXAMPLE 2 (P2) Phosphorus : 0.320% Carbon : 0.022% Silicon : 0.028 % Manganese : 0.046 % Sulphur : 0.017 % Copper : 0.030 % all by weight and rest is iron. EXAMPLE 3 (P3) Phosphorus : 0.490% Carbon : 0.028% Silicon : 0.028% Manganese : 0.046 % Sulphur : 0.017 % Copper : 0.030 % all by weight and rest is iron. In the above three corrosion resistant phosphoric iron samples, the phosphorous content is high, carbon content is less, manganese content is also less in comparison to modern steel used for concrete reinforcement. Presence of phosphorus provides corrosion resistant, in form of phosphate in concrete. Presence of low carbon, in the range of 0.02-0.028 %, helps in restricting brittle effect of phosphorus due to site competition effect. Thus, ductility similar to commercial rebar has been obtained for P1 and P2 in the present invention. However, sample P3 had failed in brittle manner. Manganese increases strength of the modern steel rebar. But phosphorus provides strength in phosphoric iron and hence even low manganese content, phosphoric iron also exhibit good yield strength and ultimate tensile strength. The corrosion performances of the above three samples, of the present invention have been compared with two reference steel bars (rebar). (i) Mild steel bar commercially called as TATA TISCON rebar and (ii) High copper containing corrosion resistant steel bar commercially called as TATA CRS rebar. TATA TISCON contain (in wt. %) 0.17-0.24 % carbon, 0.04-0.045 % phosphorus, -0.05 % Si, 0.7-0.11 % Mn, -0.024 % S, -0.006 % Cu and balance Fe. TATA CRS contain 0.17-0.24 % carbon, 0.07- 0.09 % phosphorus, 0.35 -0.5 % Cu, -0.05 % Si, 0.7-0.11 % Mn, ~ 0.024 % S and balance Fe. It has been observed that the corrosion resistance of phosphoric irons of the present invention is similar to high copper containing corrosion resistant steel bar TATA CRS and quite higher than the TATA TISCON by following studies: Potentiodynamic polarization studies of a scan rate of 0.5 mV/ s and electrochemical impedance studies (EIS) from 100 kHz to 10 mHz were carried out in pore solution of saturated calcium hydroxide of pH 12 for phosphoric iron samples P1, P2, P3 and also for TATA TISCON and TATA CRS. The potentiodynamic polarization curves in simulated saturated calcium hydroxide pore solution of pH 12 containing different concentrations of chloride ions have been shown in Figure 1 of the accompanying drawings and variation of passive film break down potential as a function of chloride concentration is shown in Figure 2 of the accompanying drawings. The pitting potentials for each sample in the saturated Ca(OH)2 pore solution containing different chloride concentrations are calculated from the potentiodynamic polarization curves in Figure 1 (a to (c) of the accompanying drawings and are plotted in Figure 2 of the accompanying drawings. The pitting potential or passive film break down potential (Eb) in Figure 1 of the accompanying drawings, indicate that unlike TATA TISCON, phosphoric iron P1 and TATA CRS are resistant to chloride ion to similar extent which shown in Figure 2 of the accompanying drawings. However, corrosion current of TATA CRS increases with increasing chloride concentrations unlike phosphoric irons. Figure 2, of the accompanying drawings reveals that pitting potential or passive film break down potential (Eb) remains almost constant with increasing chloride concentration up to certain critical value for P1 and TATA CRS while it is quite low for TATA TISCON. In the carbonated pore solution of 0.3M NaHCO3 + 0.1M Na2CO3 solution of pH 9, phosphoric iron P1 also shows higher passive film break down potential similar to the corrosion resistant steel TATA CRS and higher than that of the TATA TISCON. The Electrochemical Impedance Spectroscopy Studies, the variation of polarization resistance found by modeling from electrochemical impedance studies have been plotted in Figure 3 of the accompanying drawings. Polarization resistance for phosphoric irons and TATA CRS increases as a function of time in pore solution containing 0.1% C1-, and remain almost constant after 126 hours while it decreases for TATA TISCON. These results indicate that passive film of TATA TISCON rebar is getting destroyed more and more with time. For phosphoric irons and TATA CRS, the thickness of passive film is increasing with time and remains almost constant after 126 hours. Phosphoric irons P2 and P3 similar to P1 and TATA CRS also show higher passive film breakdown potential than TATA TISCON in potentiodynamic test. Again by electrochemical impedance Spectroscopy, similar increasing trend of Rp values with time had been observed as it was for TATA CRS. From these observation, beneficial corrosion inhibiting effect of phosphorus in phosphoric iron samples can be understood. For TATA CRS, Cu probably shows beneficial corrosion inhibiting effect. A corrosion resistant phosphoric iron steel bar is prepared from the above corrosion resistant phosphoric samples. Some of these corrosion resistant phosphoric iron samples are mentioned in the following paragraphs but these are not the only compositions possible. These are given as illustrations only and many more samples are possible to prepare in the light of descriptions disclosed here. Those verse in the art can easily vary the constituents of the samples. We Claim: 1. A corrosion resistant phosphoric iron for concrete embedment and reinforcement comprising: Phosphorus : 0.110-0.490% Carbon: 0.020-0.028% Silicon: 0.020-0.029% Manganese : 0.010 - 0.047 % Sulphur: 0.0 10 -0.018% Copper: 0.004 - 0.031 % all by weight and rest is iron. 2. A corrosion resistant phosphoric iron for concrete embedment and reinforcement as claimed in claim 1, wherein Phosphorus: 0.110% Carbon: 0.025% Silicon: 0.028 % Manganese: 0.046 % Sulphur: 0.017% Copper : 0.030 % all by weight and rest is iron. 3. A corrosion resistant phosphoric iron for concrete embedment and reinforcement as claimed in claim 1, wherein Phosphorus : 0.320% Carbon: 0.022% Silicon: 0.028 % Manganese: 0.046 % Sulphur: 0.017% Copper : 0.030 % all by weight and rest is iron. 4. A corrosion resistant phosphoric iron for concrete embedment and reinforcement as claimed in claim 1, wherein Phosphorus: 0.490% Carbon: 0.028% Silicon: 0.028% Manganese: 0.046 % Sulphur: 0.017% Copper: 0.030 % all by weight and rest is iron.

Full Text

FIELD OF INVENTION:
The present invention relates to the area of reinforcing steel/ embedment, which is corrosion resistant in concrete e.g. Buildings, Bridges and other civil works.
PRIOR ART:
Corrosion degradation of reinforcing steel/embedment in concrete is of great concern because it is the most widespread cause of degradation of reinforced concrete structures. The prevalent practice to overcome this problem of reinforcement corrosion is by using corrosion resistant steel bar, which is costly and contain copper, chromium, molybdenum and vanadium in small amount. Following are some inventions where costly elements are used to get corrosion resistant steel bar.
JP3020441, discloses a salt-resistant reinforcing steel bar for preventing the deterioration of concrete contains 0.001 to 0.1% C, 0.01 to 0.05% Si, 0.01 to such as sea salt grains and sea water splashes penetrating into a concrete wall and the generation of cracks in concrete.
JP5 8077552, discloses a salt resistant steel bar for reinforced concrete consists of, by weight, =l% kind of rare earth element and the balance Fe with inevitable impurities. The steel bar has superior resistance to corrosion due to salt in concrete.
JP58077551, discloses a steel bar consists of, by weight JP61284552, discloses an iron reinforcing rod for reinforced concrete is made of a composition containing by weight, 0.001-1.0% C, JP62188754, discloses a reinforcing steel bar having superior corrosion resistance, is composed of, by weight, 0.01-0.4% C, 0.05-2% Si, 0.3-2% Mn, 0.3-5% Cr, 0.5-1.5% Cu, 0.001-0.05% Al, one or more among 0.01-1.5% Ni, 0.01-0.3% Mo and 0.01-0.3% V and the balance Fe with inevitable impurities. The composition may further contain 0.01-0.05% P.
JP62199748, discloses reinforcing steel rod in a reinforced concrete structure installed at the seaside or in the sea is made of a steel having a composition containing by weight, JP2170945, discloses a reinforcing steel, to drastically delay its corrosion caused by salt in the free condition of Cl; the reinforcing steel bar containing by weight, 0.01 to 1.0% C, >0.05 to 0.18% Si, 0.01 to 0.3% Mn, or two kinds among Nb, V and Ti or furthermore, 0.01 to 0.3% Cu are added to the composition.
JP3183740, discloses a composition of a reinforcing bar, which contains by weight 0.001 to 1.0% C, 0.01 to 0.05% Si, 0.01 to JP3020441: discloses a salt-resistant reinforcing bar for preventing the deterioration of concrete, which contains by weight 0.001 to 0.1% C, 0.01 to 0.05% Si, 0.01 to .
STATEMENT OF INVENTION:
The presence of costly elements as disclosed in the prior art, the reinforcing steel/embedment becomes costly. The reinforcing steel/embedment produced in the instant invention is cheaper and affordable. So, the present invention relates to a corrosion resistant phosphoric iron for concrete embedment and reinforcement comprising:
Phosphorus : 0.110-0.490%
Carbon : 0.020-0.028%
Silicon : 0.020-0.029%
Manganese : 0.010 - 0.047 %
Sulphur : 0.010 - 0.018 %
Copper : 0.004 - 0.031 % all by weight
and rest is iron.
Three corrosion resistant phosphoric iron samples were
prepared to compare their efficacy with TATA TISCON and
TATA CRS, which are readily available in the market. The
constituents of these corrosion resistant phosphoric iron samples
are:
EXAMPLE 1 (P1)
Phosphorus : 0.110%
Carbon : 0.025 %
Silicon : 0.028%
Manganese : 0.046 %
Sulphur : 0.017%
Copper : 0.030 % all by weight and
rest is iron.
EXAMPLE 2 (P2)
Phosphorus : 0.320%
Carbon : 0.022%
Silicon : 0.028 %
Manganese : 0.046 %
Sulphur : 0.017 %
Copper : 0.030 % all by weight and
rest is iron.
EXAMPLE 3 (P3)
Phosphorus : 0.490%
Carbon : 0.028%
Silicon : 0.028%
Manganese : 0.046 %
Sulphur : 0.017 %
Copper : 0.030 % all by weight and
rest is iron.
In the above three corrosion resistant phosphoric iron samples, the phosphorous content is high, carbon content is less, manganese content is also less in comparison to modern steel used for concrete reinforcement.
Presence of phosphorus provides corrosion resistant, in form of phosphate in concrete. Presence of low carbon, in the range of 0.02-0.028 %, helps in restricting brittle effect of phosphorus due to site competition effect. Thus, ductility similar to commercial rebar has been obtained for P1 and P2 in the present invention. However, sample P3 had failed in brittle manner. Manganese increases strength of the modern steel rebar. But phosphorus provides strength in phosphoric iron and hence even low manganese content, phosphoric iron also exhibit good yield strength and ultimate tensile strength.
The corrosion performances of the above three samples, of the present invention have been compared with two reference steel bars (rebar). (i) Mild steel bar commercially called as TATA TISCON rebar and (ii) High copper containing corrosion resistant steel bar commercially called as TATA CRS rebar. TATA TISCON contain (in wt. %) 0.17-0.24 % carbon, 0.04-0.045 % phosphorus, -0.05 % Si, 0.7-0.11 % Mn, -0.024 % S, -0.006 % Cu and balance Fe. TATA CRS contain 0.17-0.24 % carbon, 0.07-
0.09 % phosphorus, 0.35 -0.5 % Cu, -0.05 % Si, 0.7-0.11 % Mn, ~ 0.024 % S and balance Fe.
It has been observed that the corrosion resistance of phosphoric irons of the present invention is similar to high copper containing corrosion resistant steel bar TATA CRS and quite higher than the TATA TISCON by following studies:
Potentiodynamic polarization studies of a scan rate of 0.5 mV/ s and electrochemical impedance studies (EIS) from 100 kHz to 10 mHz were carried out in pore solution of saturated calcium hydroxide of pH 12 for phosphoric iron samples P1, P2, P3 and also for TATA TISCON and TATA CRS.
The potentiodynamic polarization curves in simulated saturated calcium hydroxide pore solution of pH 12 containing different concentrations of chloride ions have been shown in Figure 1 of the accompanying drawings and variation of passive film break down potential as a function of chloride concentration is shown in Figure 2 of the accompanying drawings.
The pitting potentials for each sample in the saturated Ca(OH)2 pore solution containing different chloride concentrations are calculated from the potentiodynamic polarization curves in Figure 1 (a to (c) of the accompanying drawings and are plotted in Figure 2 of the accompanying drawings. The pitting potential or passive film break down potential (Eb) in Figure 1 of the accompanying drawings, indicate that unlike TATA TISCON, phosphoric iron P1 and TATA CRS are resistant to chloride ion to similar extent which shown in Figure 2 of the accompanying drawings. However, corrosion current of TATA CRS increases with increasing chloride concentrations unlike phosphoric irons. Figure 2, of the accompanying drawings reveals that pitting potential or passive film break down potential (Eb) remains almost constant with increasing chloride concentration up to certain
critical value for P1 and TATA CRS while it is quite low for TATA TISCON.
In the carbonated pore solution of 0.3M NaHCO3 + 0.1M Na2CO3 solution of pH 9, phosphoric iron P1 also shows higher passive film break down potential similar to the corrosion resistant steel TATA CRS and higher than that of the TATA TISCON.
The Electrochemical Impedance Spectroscopy Studies, the variation of polarization resistance found by modeling from electrochemical impedance studies have been plotted in Figure 3 of the accompanying drawings. Polarization resistance for phosphoric irons and TATA CRS increases as a function of time in pore
solution containing 0.1% C1-, and remain almost constant after 126 hours while it decreases for TATA TISCON.
These results indicate that passive film of TATA TISCON rebar is getting destroyed more and more with time. For phosphoric irons and TATA CRS, the thickness of passive film is increasing with time and remains almost constant after 126 hours. Phosphoric irons P2 and P3 similar to P1 and TATA CRS also show higher passive film breakdown potential than TATA TISCON in potentiodynamic test. Again by electrochemical impedance Spectroscopy, similar increasing trend of Rp values with time had been observed as it was for TATA CRS.
From these observation, beneficial corrosion inhibiting effect of phosphorus in phosphoric iron samples can be understood. For TATA CRS, Cu probably shows beneficial corrosion inhibiting effect.
A corrosion resistant phosphoric iron steel bar is prepared from the above corrosion resistant phosphoric samples.

Some of these corrosion resistant phosphoric iron samples
are mentioned in the following paragraphs but these are not the
only compositions possible. These are given as illustrations only
and many more samples are possible to prepare in the light of
descriptions disclosed here. Those verse in the art can easily vary
the constituents of the samples.

We Claim:
1. A corrosion resistant phosphoric iron for concrete embedment and reinforcement
comprising:
Phosphorus : 0.110-0.490%
Carbon: 0.020-0.028%
Silicon: 0.020-0.029%
Manganese : 0.010 - 0.047 %
Sulphur: 0.0 10 -0.018%
Copper: 0.004 - 0.031 % all by weight
and rest is iron.
2. A corrosion resistant phosphoric iron for concrete embedment and reinforcement as
claimed in claim 1, wherein
Phosphorus: 0.110%
Carbon: 0.025%
Silicon: 0.028 %
Manganese: 0.046 %
Sulphur: 0.017%
Copper : 0.030 % all by weight and
rest is iron.
3. A corrosion resistant phosphoric iron for concrete embedment and reinforcement as
claimed in claim 1, wherein
Phosphorus : 0.320%
Carbon: 0.022%
Silicon: 0.028 %
Manganese: 0.046 %
Sulphur: 0.017%
Copper : 0.030 % all by weight and
rest is iron.
4. A corrosion resistant phosphoric iron for concrete embedment and reinforcement
as claimed in claim 1, wherein
Phosphorus: 0.490%
Carbon: 0.028%
Silicon: 0.028%
Manganese: 0.046 %
Sulphur: 0.017%
Copper: 0.030 % all by weight and
rest is iron.

Documents:

1823-DEL-2005-Abstract-(29-06-2011).pdf

1823-del-2005-abstract.pdf

1823-DEL-2005-Claims-(07-05-2012).pdf

1823-DEL-2005-Claims-(29-06-2011).pdf

1823-del-2005-claims.pdf

1823-del-2005-Correspondence Others-(03-05-2012).pdf

1823-DEL-2005-Correspondence Others-(07-05-2012).pdf

1823-DEL-2005-Correspondence Others-(29-06-2011).pdf

1823-del-2005-correspondence-others.pdf

1823-DEL-2005-Description (Complete)-(29-06-2011).pdf

1823-del-2005-description (complete).pdf

1823-DEL-2005-Drawings-(29-06-2011).pdf

1823-del-2005-drawings.pdf

1823-del-2005-Form-1-(03-05-2012).pdf

1823-del-2005-form-1.pdf

1823-DEL-2005-Form-2-(29-06-2011).pdf

1823-del-2005-form-2.pdf

1823-del-2005-form-3.pdf

1823-del-2005-GPA-(03-05-2012).pdf

1823-DEL-2005-GPA-(07-05-2012).pdf

1823-DEL-2005-GPA-(29-06-2011).pdf

1823-del-2005-Petition-137-(03-05-2012).pdf

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Patent Number

253452

Indian Patent Application Number

1823/DEL/2005

PG Journal Number

30/2012

Publication Date

27-Jul-2012

Grant Date

23-Jul-2012

Date of Filing

14-Jul-2005

Name of Patentee

INDIAN INSTITUTE OF TECHNOLOGY KANPUR

Applicant Address

KANPUR-208016, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	BALASUBRAMANIAM R.	MME DEPARTMENT, INDIAN INSTITUTE OF TECHNOLOGY, AN INDIAN INSTITUTE OF KANPUR-208016, INDIA
2	SAHOO GADADHAR	MME DEPARTMENT, INDIAN INSTITUTE OF TECHNOLOGY, AN INDIAN INSTITUTE OF KANPUR-208016, INDIA

PCT International Classification Number

C23C 28/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA