COATINGS FOR STEEL & CONCRETE Purpose : Concrete to be protected for chloride attack in aggressive environment (marine/Industrial area)

STEEL SELECTION & COATINGS Corrosion resistant steel reinforcement Bass (CRS bars) Method developed by CECRI (Central Electro Chemical Research Institute Karaikudi, TN) Inhibited cement slurry coating system Cement polymer composite coating system

Fusion bonded epoxy coated rebar (FBECR) Hot dip galvanizing Epoxy - phenolic Interpenetrating polymer network (IPN) coating Truncated inhibited slurry cement base coating (used in KRCL)

CORROSION RESISTANT STEEL SAIL – HCR bass TISCO – TISCON – CRS - TISCON – TMT They have dual micro structure with inter surface tempered & at outer surface Ni, Chromium, Copper & Phosphorous also added.

CEMENT SLURRY COATING Derusting – Dipping in acidic, alkaline, water Phosphating – phosphate jelly for temp protection between de-rusting and cement slurry coating Cement slurry – 2 coats of OPC cement slurry & inhibitor solution Cost 2000-3000/MT

CEMENT – POLYMER COMPOSITE COATING SYSTEM (CPCC) Surface preparation – sand blasting Coating – one coat of Rapid setting primer (dipping or brush) After 30 minutes – cement polymer sealing coat Dried for 6 hours Cost 3200-8000/MT

FUSION BONDED EPOXY COATING (FBEC) Degreasing & Cleaning by shot blasting or grit blasting Heating – Approx temp 2300 Coating – Bar fed in coating bath where epoxy powder sprayed electrostatically. Epoxy powder melts, flows, gels, cures, cools and produces uniform coating Forced cooling by water spray Cost 4500-13000/MT

HOT DIP GALVANISING Galvanising is the process of deposition of zinc over surface of rebars Removal of oil, grease etc by dipping into caustic solution & rising Scale rust removed by pickling in H2SO4/HCL & rising with clean water OR Sand blasting done alternatively Immerse bars in molten zinc (98.5% pure) at specified temp of 450C Rebars dried Successful where carbonation risk is there but not suitable for chloride attach.

TURNCATED INHIBITED CEMENT SLURRY COATING FOR DRY CLIMATE Partial CECRI system Cost = 500/per MT Clean by wire brush etc One coat cement slurry (1 kg cement + 600 cc of inhibitor solution) by dipping or brushing Dry for 24 hrs in shade 2nd similar coat and dry for 24 hrs in shade

RECOMMENDED COATING FOR CONCRETE Aggressive environment (Sieve, VS, Exten) Non aggressive environment Important structure Other structure (Mild/Moderate) Cement – polymer composite crating(CPCC) OR CPCC OR Turncated inhibited cement slurry coating Fusion bonded Epoxy crating Inhibited cement slurry coating

1st coat of IPN by brush/spray 2nd coat with 4-8 hem Cured for 48 hrs EPOXY PHENOLIC IPN (INTERPENETRATING POLYMER NETWORK) (Developed by CBRI Roorkee) Sand blasting 1st coat of IPN by brush/spray 2nd coat with 4-8 hem Cured for 48 hrs Epoxy phenolic ipn Part A – Resin component Part B – hardener component Added 1:1 by volume & vigorous stirred for 5-10 minutes

COATINGS FOR CONCRETE Epoxy phenolic IPN Crating Integrated 4 – coat system – CECRI Epoxy coating Coal tar coating

EPOXY IPN COATING Preparation of IPN polymers Two different resins A medium viscosity epoxy resin An aromatic armine Cross linked & phonotic resin obtained

INTEGRATED FOUR COAT SYSTEM Epoxy polyamide Iron oxide – 1st coat Epoxy polyamide MiO – 2nd coat (porous) Epoxy polyamide TiO2 – 3rd coat Epoxy polyamide aliphatic – 4th coat (tough polymer) Cost – 320/M2

EPOXY COATING Thickness of coating – 8 to 15 Curing by amines or polyamides They are classified as under Solvent base epoxy Thin thixotropic liquid epoxy based primer Thick epoxy coating applied by spray.

COAL TAR FOR EPOXY They have properties of both coaltar & epoxy Good adhesion with concrete & chemical resistant Two coats (total thickness 150 – 200 u) applied by rollers or airless spray.

SELECTION OF CONCRETE COATING Aggressive Non aggressive Sub structure – coal tar epoxy Not required Super structure – Epoxy phenolic IPN or CECRI four coat Blended cement can be used Dense concrete with sufficient cover enough Clean R/f bar be used.