corrosion of steel

Corrosion of SteelJSPL - Marketing

17.10.2010

Copyright © 2010 Jindal Steel & Power Ltd.2

Process of Corrosion• Corrosion of metals is an electrochemical process, involves transfer of charge

from one species to another• For corrosion to occur, there must be two half cell reactions, one capable of

producing electrons (anodic reaction) and the other capable of consuming them (cathodic reaction)

• For corrosion of steel, the anodic reaction can be

• And the cathodic reactions can be

Copyright © 2010 Jindal Steel & Power Ltd.

Causes of Corrosion• Steel in concrete is usually in a noncorroding, passive condition

• However, steel is often used in severe environments where sea water or deicing salts are present

• When chlorides moves into the concrete it disrupts the passive layer protecting the steel, causing it to rust and pit

• Carbonation is another cause of steel corrosion, when concrete carbonates to the level of the steel rebar, the normal alkaline environment which protects the steel form corrosion is replaced by a more neutral environment

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Effects of Corrosion• The formation of rust leads to a loss of

bond between the steel and concrete• Corrosion of steel produces a bulky

reaction product with volume 7-8 times that of steel

• This puts pressure on the surrounding concrete cover which first cracks and eventually spalls

• Extensive corrosion of the steel can lead to mechanical weakening of the reinforced structure

• The ultimate result can be collapse of the structure

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Methods for Prevention of Corrosion


Pure Steel• Usage of pure steel which is free of

impurities makes it resistive to corrosion

• An example of such structure using pure steel is the Iron Pillar in New Delhi which hasn’t corroded for hundred of years

• Pure steel, though resistant to corrosion, will not be strong enough to be used in structures as the impurities added increase the structural strength of steel

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Cathodic Protection• The steel rebar are coupled with with

reactive metals such as Cu, Zn etc.• This creates negative charge on the

rebar• The OH- ions that are produced are

attracted towards the anode made of Cu or Zn

• Thus the reactive metal is corroded and the steel is protected

• This method provides non uniform resistance to corrosion and the steel further away from anode is corroded

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Epoxy coated rebar• A fusion based epoxy coating is applied

to steel rebar through shot blasting• The epoxy coating acts as a protective

layer and prevents the corrosion of steel• But epoxy coating of rebar reduces the

bond strength between concrete and steel

• The epoxy coating can be easily damaged during transportation and handling, the exposed steel can corrode under the coating

• The epoxy coating of rebar is expensive and increases the costs by approx. Rs. 8-10 thousand per ton

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Galvanized Rebar• Galvanized rebar have a protective layer of

zinc metal• The zinc coating serves as a barrier to

corrosive elements that the rebar is exposed to when embedded in concrete

• It also provides a level of cathodic protection where the zinc will preferentially corrode when in contact with bare steel

• But galvanizing also reduces the bond strength between rebar and concrete

• The steel is exposed below zinc coating during cutting and bending

• Galvanizing of rebar is expensive and costs around Rs. 4000 per ton

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Stainless Steel Rebar • Stainless steel rebar have inherently good

corrosion resistance• They don’t have the any coatings which can

chip, crack or degrade and cause corrosion• Capable of withstanding shipping, handling

and bending• However, the mechanical properties of

stainless steel are not at par with construction grade steel (strength ~216MPa)

• Due to reduced strength, the quantity of steel used is increased

• The stainless steel rebar are prohibitively expensive and hence are not widely used

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Fiber Rebar • These rebar are made from fiber-

reinforced plastic• The material used for fabrication of rebar

is resistant to corrosion• But it has lower bonding strength with

concrete compared to that of steel as grip is provided by epoxy coating

• The strength of the material is also lower than that of steel

• Fiber rebar is are relatively new and therefore are prohibitively expensive

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Corrosion Resistant Steel (CRS) Rebar• CRS rebar are inherently resistant to corrosion• They are manufactured b y adding 0.5% of

Copper, Nickel or Chromium to increase the resistance

• CRS rebar are only Rs. 2-2.5K expensive than normal rebar and can double the life of structure under harsh conditions

• The rebar can withstand rough handling and transportation; can be cut and bend without lowering their resistance to corrosion

• The mechanical properties of CRS rebar is at par with normal rebar

• Use of CRS Rebar can provide a cost saving of 4-5% with welding

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JSPL TMT Rebar


JSPL – Patratu, Jharkahnd• The company Is setting up a 6.0 MTPA Steel Plant and 1609 MW

Captive Power Plant (CPP) at Patratu• The plant facilities for the first phase include a 0.6 MTPA wire

rod mill and 1 MTPA rebar mill• JSPL has started production of rebar from it’s Rebar mill at

P:atratu using steel that is being manufactured from the mother plant at Raigarh

• As JSPL has complete control over the steel making and rolling process, the quality of the rebar produced is superior to that being by produced by secondary producers and even some primary producers

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JSPL Rebars• JSPL rebars are hot rolled and subjected to

online Thermo mechanical Treatment (TMT) in state of the art rolling mill from Morgan Construction (now Siemens)

• The Rebars comply with BIS 1786:2008• The rebars are available in sizes

6,8,10,12,16,20,25,28,32,36,40 mm• The Rebars are produced in Fe500D, CRS

and Fe550 grades

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Advantages of JSPL Rebar• Due to a controlled manufacturing

process, JSPL rebars have excellent bendability

• A higher strength property is imparted by controlling the parameters of Thermo-Mechanical Treatment to ensure superior weld ability

• JSPL rebars have uniform and precise ribs leading to uniform bond strength

• Higher strength and elongation helps economize the steel consumption

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Thank you

corrosion of steel

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