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

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 enoughClean R/f bar be used.