SRMB SRIJAN PRIVATE LIMITED (formerly called The Steel Rolling Mills of Bengal Limited.) was established in 1951. A state-of-art rolling mill was installed and commissioned by Nippon Steel Corp. of Japan. SRMB SRIJAN PRIVATE LIMITED is the first company (in Secondary Steel Sector) to manufacture Thermo Mechanically Treated (TMT) bars using the latest technology available worldwide. TMT Plant supplied and commissioned by Hennigsdorfer Stahl Engineering Gmbh, Germany in 2000. SRMB SRIJAN PRIVATE LIMITED is the pioneer to introduce 'X' ribs on Fe 500, IS 1786 grade steel under the brand name of SRMB 500+ having superior mechanical and corrosion resistance properties than any other existing same grade steel in market, and continuing its path of innovation, SRMB SRIJAN PRIVATE LIMITED now introduces SRMB AZAR, a corrosion resistant rebar to Indian consumers at Indian prices in technical collaboration with M/S John Galt Zinga Technologies, who are authorized sole representative of M/S ZINGA METALL BVBA, Belgium, in India. This rebar is better than any corrosion resistant rebar (e.g., hot-dip galvanized / epoxy coated / Cu-Cr alloyed CRS) and owing to its latest corrosion resistant technology it can prolong the life of civil structures beyond 125 years.
SRMB - A TRUST
Every meter of our TMT bars are embossed with "SRMB" mark to ensure you to get the right material with all the promises we have made to you. Please ensure you get what you wanted, by looking for the "SRMB" mark. SRMB family believes in providing complete mild steel product of all the grades, i.e., Fe 415, Fe 500, Fe 550, having a new, better and innovative corrosion resistance property with highly cost effective in comparison to the alternate products available in the market. The novel pioneer product SRMB AZAR having an outstanding formula for corrosion resistance will create a new generation to the construction industry. We have a unique R&D /Q. C. department for continuous product development / improvement and implementation of best international practices with real time logistics support provided by qualified and experienced professionals (Metallurgists/Chemists in corrosion control and product development).
Characteristic of Zinga coating on SRMB Azar
Zinc used in the Film Galvanisation or zinganisation process is produced by a special atomization process which provides its unique particle size and structure, quality and purity.
The Zinc atomized particles are in flake form, which ensure zero porosity in the applied coating.
The polymerized coating contains 96% of guaranteed Zinc film in a dry thickness which has a purity of 99.995%.
The zinga coating on SRMB AZAR is a one component zinc compound.
As the Zinga layer is metallic in nature it has a similar co-efficient of thermal expansion because of which temperature changes does not cause cracking in the coating.
The Zinga layer is composed of metallic / non-metallic components and bonds with the concrete like the underlying base metal does.
Zinga coating has a physical (electro-mechanical) bond with the steel. A potential of (-)1060mV develops between the Zinga and steel.
Zinga reacts with fresh concrete to form:
Impervious layer of Zinc Hydroxyl Chloride (ZHC) and organic binder. Thus the charge transfer reactions at the interface, is completely stopped.
Rough interface between Zinga coat and concrete, which offers better adhesion between SRMB AZAR and concrete.
Zinga corrosion products occupy smaller volume thus minimizing build-up of internal stresses in the concrete. The corrosion products also migrate into the concrete matrix, thus blocking the pores of the concrete.
Zinga coating on SRMB AZAR is fireproof (certified BS476 parts 6&7). This means that a dry Zinga coating on SRMB AZAR will neither propagate fire nor cause one to spread.
Film Galvanizinzation (Zinganization) Parameter
|Coating process made available by John Galt Zinga Technologies|
|Surface (of Rebar) Preparation||Shot blasted following the standard Sa 2.5|
|Method of Application||Applied by airless spray system|
|Layer thickness maintained||30 ± 2 µm DFT|
|Drying time allowed||10 minutes (Touch-dry)
48 hours (For complete mechanical cure)
|Post treatment||Misted with cold water|
Comparison with Others
Comparison of SRMB AZAR with Hot-Dip Galvanized, Fusion Bonded Epoxy Coated and CRS Reinforcement Bar
Hot-Dip Galvanized (HDG) rebar
|Coating type||Single Pack,Zn rich coating solvent based aromatic hydrocarbons||3 Layers of Zn-Fe alloy metallurgically bonded to each other and ultimatly to the base steel||Fusion Bonded Powdered epoxy coating||No coating Catastrophic failure due to severe pitting*|
|Zinc Content||96% (in DFT), pure to 99.995%||75% – 85%, pure to 98%||Nil||Nil|
|Reloading Possibility with other paints||Yes||No||No||Not applicable|
|Possibility of Welding (X Ray standard)||OK||OK, with limitations||No||Ok|
|Hydrogen induced cracking to load bearing welds||No||Yes||Not applicable||Yes|
|Cathodic Protection||Excellent||Excellent||No||Not applicable|
|pH Tolerance||pH 4 - pH 12.5||pH 9 - pH 12.5||pH 5.5 - pH 9||pH10 - pH11|
|Nature of Bond (of coating)
a) with rebar b) with Concrete
Metallurgical bond Good
No such bond Poor
Not applicable Excellent
a) Shaping (Bending)
b) Cyclic vibration resistance
c) Transportation & Storage
|Excellent No damage/crack Unlimited Normal Care||Poor Can damage/crack Limited Normal Care||Poor Can damage/crack Limited Special Care||Not applicable|
|Abrasion Resistance||Very Good||Good||Low||Not applicable|
|Thermal Expansion||No damage / crack of coating with stress induced thermal cycling||Can Damage / Crack with stress induced thermal cycling||Can Damage / Crack with stress induced thermal cycling||Not applicable|
|Biological Attack||Excellent Resistance||Less resistant than SRMB AZAR||Susceptible||Susceptible|
|Cost Effectiveness||SRMB AZAR is 30% more cost effective compared to HDG rebar and15% more cost effective compared to FBE coated rebar.|
|Life expectancy||125 years +||50 years||30 years||30|
*Ref. P. Albrecht and A. H. Naeernt, 1984, Performance of weathering steel in bridges, National Co-operative Highway Research Program Report 272, Transportation Reserach Board (Washington, D.C. National Resarch Council)
Corrosion rate of various type of reinforcement bars under different test conditions (Temp. : 30 ± 2°C)
|Type of Tests||SRMB AZAR||HDG rebar||FBEC rebar||CRS rebar|
Corrosion Rate in µmpy
Corrosion Rate in µmpy
|Corrosion Rate in µmpy
(Static immersion Test in 3.5% NaCl solution, Test Duration : 90 days) Carried out by : RDCIS, SAIL, Ranchi (RD/CACE/SRMB-06)
|Pitting resistance tendency
(in concrete pore solution with 3.5% NaCl solution) Epit, mV (SCE) Loop Area
Carried out by : NML, Jamshedpur (SSP 0289/06)
The corrosion cycle of an uncoated steel rebar begins with rust expanding on the surface of the bar and causing cracks near the steel / concrete interface. As time passes, the corrosion products build up, resulting in more extensive cracking until the concrete eventually breaks away from the bar, causing spalling.
There are three stages in the corrosion model for concrete embedded steel – incubation, Initiation and Propagation, Corrosion rates at the propagation stage are significantly accelerated once the concrete cover has cracked due to rust formation.
National Loss Due to Corrosion
The direct loss due to lack of corrosion control in India is around Rs. 30,000 crores per annum. Indirect losses including the toll in human lives runs into double that figure. An enormous number of civil structures in India are in crying need of repair because of corrosion eating away at their core. Rehabilitation cost is added to lifetime cost. India is globally competitive in anti-corrosion technology but this is not fully utilized at the applicator level because of a variety of reasons including lack of knowledge. Corrosion needs to be controlled using the latest corrosion protection techniques available.
Convetional Anti-corrosion Technology Fails to Protect
Traditional corrosion preventive measures such as hot-dip galvanizing, fusion bonded epoxy coating, other hard coatings of polymers or the use of CRS, HCRM etc., prove to be ineffectual protection for reinforcement bars in the long run. These techniques will keep the concrete safe and sound only during the initial incubation period of about 30 years.
Fusion Bonded Epoxy Coating
Process: In the powder coating process, a dry powder is applied to a clean surface. After application, the coated object is heated, fusing the powder into a smooth, continuous film. Powders are available in a wide range of chemical types, coating properties and colors. The most widely used types include acrylic, vinyl, epoxy, nylon, polyester and urethane. Modern application techniques for applying powders fall into four basic categories: fluidized bed process, electrostatic bed process, electrostatic spray process and plasma spray process. The electrostatic spray process is the most commonly used method of applying powders. In this process, the electrically conductive and grounded object is sprayed with charged, non-conducting powder particles. The charged particles are attracted to the substrate and cling to it. Oven heat then fuses the particles into a smooth continuous film. Coating thickness in the range of 25 to 125 micrometers (1 to 5 mils) are obtained. Controlling a low film thickness is difficult. A booth and collection system can be used to collect over spray for re-use.
The fusion bonded epoxy coated rebar (FBECR) was developed in United States in 1960s and its use was strongly recommended in coastal areas. It was claimed that FBECR owing to the dielectric property imparted resistance to the permeation of moisture and aggressive anions (such as chloride ions) and functioned as an electrical insulator to provide physical barrier between the steel bars and corrosive electrolytes. Based on these claims, the FBECR became extremely popular in USA in eighties and a National standard for the application and acceptability of this coating on rebars was formulated. Thereafter, the production and use of FBECR also started in many other countries.
Unfortunately, the sign of distress of structures having FBECR as reinforcement started appearing within 10 years of their erection. Many of other findings had also established that FBECR was not a foolproof technique and perhaps more dangerous in causing localized corrosion of reinforcement bars than the uncoated steel bars. It was reported that in 95% of the cases of bridge decks, the epoxy coating had de-bonded from the steel surface before chloride arrived and did not provide any additional service life. The investigations revealed that these failures took place either at the defect sites of the coating or at the places where although the coating was intact but corrosion took place under coating. These observations created great concern and had cast doubt on the ability of FBECR to withstand the corrosive attack of chloride-contaminated concrete. This led researchers to have a re-look on the performance of FBECR.
The published research papers attributed the causes of unexpected failures of FBEC either to existence of defects in coating prior to embedding in concrete or to the contaminated surface prior to the application of the coating. The one very vital aspect that has not attracted the attention of researchers is the superb performance of epoxy coatings in preventing the corrosion of pipe lines carrying neutral water that are providing useful service life even after years of their installation. This fact suggests that there exist uncomfortability of epoxy coating in contact with concrete environments.
In contrast to the common believe that FBEC resists diffusion of water through it, research work at National Metallurgical Laboratory, Jamshedpur has established that a gradual increase in uptake of water by coating takes place in neutral chloride as well in SPS (simulated concrete pore solution) but at a faster rate in the latter case. These observations indicate that the epoxy coating, when directly exposed to aqueous solution, is not resistant to the penetration of moisture and aggressive ions and presence of alkalinity at the interface accelerates the process of absorption. The rebars in contact of neutral chloride solution (3.5% NaCl), show slower corrosion rate even to that of lowest chloride ion added in SPS (0.15%). The above results indicate that in neutral sodium chloride solution, the FBECR exhibit more stable performance in comparison to chloride blended alkaline SPS solution. This was probably the reason that the introduction of FBECR as reinforcement material was strongly recommended during seventies which was based on results recorded for coated rebars exposed in neutral sodium chloride fog tests. Being a dielectric material, the epoxy coating is expected to withstand the diffusion of chloride ions through it. Diffusion of moisture through the coating, especially in alkaline concrete pore solution, which contains considerable amount of potassium ions, was quite fast. These ions may destabilize the inevitable pinholes existing in the coating and may accelerate the corrosion process.
It is experimentally established that:
FBEC is more prone to deterioration in chloride contaminated alkaline solution than neutral chloride solution.
A defect free coating is very resistant to diffusion of chloride and other ions. Moisture and oxygen, however, can penetrate through the coating but corrosion rate of substrate is aggravated only when chloride ions are present at coating-metal interface.
Propagation of corrosion underneath the coating can proceed silently without any initial indication of bleeding of concrete till the final stage of cracking of concrete occurs.
Summary of disadvantages in Fusion Bonded Epoxy Coating
Fusion-bonded Epoxy-coated rebar must be handled carefully to prevent damage to the coating. Since the coating has no cathodic protection if the coating is damaged at cut ends or scratched during handling, corrosion can start and progress unimpeded along the steel under the FBEC as if no protection exists. The full extent of the corrosion will not be visible since it proceeds under the FBEC. Repair of corrosion beneath the FBECR is difficult and expensive. In some structures, replacement or repair of rebar may be impossible.
Being a barrier type of coating, it facilitates localized pitting corrosion through pinholes. This was very much evident in the Florida Bridge by undercutting of the fusion-bonded epoxy coated reinforcing bars. Moreover, corrosion cells are set-up in the damaged area of the rebars created through poor handling during shipping and installation, which lead to first delamination of the epoxy coating then rusting. Studies published from Florida Bridge have shown that the harsh marine environments reduce the service life of the epoxy rebar significantly.
FBE rebar actually has lower bond strength to concrete than black steel.
It undergoes degradation on long-term exposure to sunlight and hence necessitates storing of the coated reinforcement under sheltered condition.
It shows generally poor alkali resistance.
It needs additional electrical interaction of the rebars to facilitate cathodic protection and other electrochemical process that may needed for then and there maintenance of the structures.
Above all, the application of fusion bonded epoxy coating needs carefully prepared surfaces. This poses difficulties in field preparation and the long-term performance is not satisfactory.
Mechanism of Corrosion Reaction on the Epoxy-Coated Rebars
The mechanism of corrosion reaction on the epoxy-coated rebars can be schematically.
Described by considering the diagram shown in above fig.1. This proposed model clearly demonstrate that in the absence of any chloride ion at substrate-coating interface, corrosion reaction should either be negligibly small or should decrease with passage of time. In absence of any chloride ion, the alkalinity of pore solution helps in strengthening of already existing passive film at the interface and no corrosion should take place. In certain favorable conditions, where oxygen and water concentration is higher, the normal reaction of stable rust formation, should take place. In the above schematic model it is proposed that migration of chloride underneath of the coating take place through the defects whereas moisture and oxygen can penetrate through the intact coating. Various steps such as water and oxygen diffusion, cationic and anionic transport, development of cathodic and anodic sites, electrochemical reactions, generation of catholytes and anolytes are required to take place prior to blistering, rusting and delamination of coatings. As reported earlier [3,4,5] the diffusion coefficients of chloride (0.47x10-11 cm2/S) and sodium (0.3x10-10 cm2/S) ions through epoxy coating are considerably less in comparison to oxygen and water (10-8). This suggests that for an intact defect free epoxy coating, the time required for reaching chloride at the metal surface is about 100 times slower than that for water. In the absence of any chloride present at the interface, the propagation of corrosion on epoxy coated rebars surface therefore has a remorse chance. The pre-requisite for corrosion caused due to chloride at the rebars surface, therefore, is that the coating should either develop cracks during service life or they remain present at the substrate surface prior to the application of the coating. The role of chloride ion in a corrosion process of rebar is simply to de-stabilize the stable g-Fe2O3 oxide phase by forming a soluble complex salt of iron. These salts are not only acidic in nature, but also act as good ionic conductor owing to their excellent conductivity. This helps in depolarization of the anodic reaction and facilitation of corrosion process. This discussion brings out the fact that if FBECR are completely defects free and no trace of chloride is present on the substrate (steel) prior to the application of the coating, the onset and propagation of corrosion reaction may take a considerable period of time. However, if defects are present, the permeation of chloride ion may take place at an alarming rate and attack will be localized in nature.
A longer duration exposure test of FBECR in concrete mortars had established that the undercoating corrosion reactions silently proceed without affecting the outer surface of the coating. To our utter surprise, the coating from out side appeared quite intact except the accumulation of rust at the pinholes (Fig.2). When the coating was removed by a sharp knife, it came out very easily in form of chips. Whole surface of the steel below the coating was covered with loose black rust (Fig.3). The epoxy coating, which was fusion bonded with steel rebars' surface, had lost the bonding with the substrate. The EDXA, SEM and XRD studies supported the view put forward that the undercoating corrosion reaction sets in FBECR. The morphology and EDXA of red rust accumulated at the pinholes' mouth showed nodular structure with strong peaks of chloride. XRD of the red rust confirmed the presence of unstable ß-FeOOH rust. The presence of strong peaks of chloride in EDXA suggested that chloride ions play active role in corrosion of FBECR.
SRMB Samachar - Zinga Work is going on at Piprakhali Bridge.
Protection in SRMB Azar
Protection against rust in SRMB AZAR - in two ways :
|Passive protection||protection by means of a barrier (organo-metallic composite film of ZHC and binder)|
|Active protection||galvanic or cathodic sacrificial Zinc (96% in dry film, 99.995% pure) anode|
Passive Protection in SRMB AZAR :
Active Protection in SRMB AZAR
Both hot-dip galvanizing and zinc thermal spraying exhibit a constant sacrificial rate of the zinc layer.
In SRMB AZAR this sacrificial rate (of zinc) reduces dramatically after the zinc layer has oxidized.
Each zinc particle within the film-galvanized layer is encased and protected by the organic binder without adversely affecting the electrical conductivity.
This enables the coating to create the same potential the zinc and the steel as hot dip galvanizing (-1060mV) but with a lower rate of zinc loss.
Underneath corrosion in Fusion bonded epoxy coated (FBEC) bar
Quality that Speaks
QUALITY THAT SPEAKS
SRMB SRIJAN Pvt. Ltd... A RETROSPECTIVE
1st TMT Manufacturer in Secondary steel sector
1st Conversion Agent of SAIL for TMT Bars
1st ISO: 9001 Company in Secondary steel sector
1st ISO: 14001 Company in Secondary steel sector
1st Licensed with ISI for ISO: 1786 for TMT bar (8mm to 12 mm diameter)
1st to introduce Fe-500 grade TMT bars on regular basis
1st to introduce "X" rib design (Has the Patent) on Fe 500, ISO : 1786 grade steel
Corresponds to the European Standards ISO 3549-1987 and DIN 55 969 (zinc concentration in the dry extract of 96%)
Corresponds to the European Standards ISO 752 and DIN 1706 (zinc purity of 99.995 %)
Conforms to U.S. ARMY SPEC. MILP - 210 35.
The only coating having dedicated to NATO No.
Approval from EIL for using zinga for corrosion protection of metallic structures and carbon steel rebar.
Approval from IOCL for trial application of zinga for corrosion protection of pipelines.
Limited acceptance from ONGC for certain applications on off shore platform
Madha Project, Mumbai
Suryalanka Retaining Wall Project.
Test reports from Universities / Institutes all over the world, as mentioned below, have clearly indicated that the protection of rebars / structures using zinga is much more effective than any other anti-corrosion systems.
University of Gent, Belgium
South African Bureau of Standards, South Africa
BNF Fulmer Research Centre, UK
Productivity and Standards Board, Singapore
National Metallurgical Laboratory, Jamshedpur
Jadavpur University, Kolkata