1. Investigation of Organic Coatings Durability
on Concrete Reinforcement Corrosion Protection with the Synergistic Influence
of Corrosion Inhibitors
S.Kalogeropoulou1, P.Pantazopoulou1, Th.Zafeiropoulou2, K. Sideris3
1. Electrical Engineering Department, Technological Educational Institute of Piraeus, Athens, Greece
2. Faculty of Chemical Engineering, National Technical University of Athens, Greece
3. Democritus University of Thrace, Dept. of Civil Engineering, Xanthi, Greece
eRA – 9, T.E.I. of Piraeus, September 2014

2. In this work the results obtained until now in the framework of an ARCHIMEDES III research project entitled "Investigation of Organic Coatings Durability on Concrete Reinforcement Corrosion Protection with the Synergistic Influence of Corrosion Inhibitors” are presented.
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3. Aim of the study
The action of various organic coatings and corrosion inhibitors in the protection of steel reinforcement in highly corrosive conditions is investigated. Five different types of organic protective coatings have been chosen to be studied: a two-pack epoxy paint, a two-pack polyurethane paint, a nanotechnology paint and two acrylic dispersions. A classification of the protective action of the organic coatings against corrosion, based on the results of various experimental methods, is presented.
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4. Reinforcement corrosion – Protection methods
Reinforcement corrosion: main cause of reduction of a structure’s life
coatings on the surface of concrete
corrosion inhibitors
cathodic protection
stainless steel reinforcement
coating of reinforcement
available
protection
methods
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5. Organic coatings Surface coatings on concrete:
prevent the deterioration by creating a physical barrier between the concrete structure and the harmful substances from the environment
improve or maintain the appearance
offer an effective and reliable solution for the protection both of the concrete and the embedded steel
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6. Desired properties of organic coatings
Good adhesion to concrete even when wet
Resistance to high alkalinity of concrete
Ability to penetrate into the pores and cracks of concrete
Good resistance to ultraviolet (UV) radiation and weathering
Good mechanical strength
Prevent entry of water but allow water vapor permeation
High resistance to the permeation of sulfur dioxide and carbon dioxide and to the penetration of chloride ions in the pores and cracks (less than 0,3 mm) of the concrete
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7. Alkanolamine-based corrosion inhibitors
Corrosion inhibitors have been successfully used as admixtures to concrete to reduce the risk of reinforcement corrosion.
Alkanolamine-based corrosion inhibitors
move through the pore structure of concrete to reach the surface of reinforcing steel, where they form a protective film
reduce chloride ion ingress into concrete
are classified as mixed inhibitors, because they influence both the cathodic and the anodic process of corrosion
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8. Degradation of coatings
Μain factors influencing the durability of coatings:
sunlight (ultraviolet radiation)
moisture
heat
Τhe result of the combination of these factors is much more serious than each factor individually.
Degradation can vary from mere surface discoloration affecting the aesthetic appeal of a product to substantial loss of mechanical properties.
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9. Properties studied and methods used
Reinforcement’s corrosion behavior
Effect of UV-radiation to coatings
Liquid water and water vapor transmission rates
Carbonation depth
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10. Reinforcement’s corrosion behavior
Use of the Strain Gauge (SG) technique, which is based on the appearance of swelling strain near the steel reinforcement in the concrete and is measured by embedded SG sensors in mortar specimens. The cause of the swelling tension is the formation of corrosion products (iron oxides, Fe3O4, Fe2O3, FeO(OH)) having greater specific volume than iron.
Determination of the gravimetric mass loss of reinforcing steel bars after a certain period of exposure in the corrosive environment. Mass loss (according to ISO/DIS 8407) is estimated as the difference between the initial and the final mass of the bars, as determined by removing the corrosion products from the bars.
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11. Effect of UltraViolet-radiation to coatings
Dry Film Thickness was measured according to ASTM D4138 “Standard Practices for Measurement of Dry Film Thickness of Protective Coating Systems by Destructive, Cross-Sectioning Means”.
Cross cut test was performed according to ISO 2409:1992(E) “Paints and varnishes – Cross cut test” and ASTM D3330 / D3330M - 04(2010) “Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape”.
In coated specimens coatings’ adhesion was measured according to BS EN 24624:1993/ BS EN ISO 4624:2003 “Paints and varnishes - Pull off test for adhesion” and ASTM D e1 “Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers”.
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12. Liquid water and water vapor transmission rates
Liquid water transmission rate of each coating is determined according to standard DIN EN : “Paints and varnishes - Coating materials and coating systems for exterior masonry and concrete - Part 3: Determination of liquid water permeability”.
Water vapor transmission rate is determined according to standard DIN EN ISO “Coating materials and coating systems for exterior masonry and concrete - Part 2: Determination and classification of water-vapor transmission rate (permeability)”.
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13. Carbonation depth
Measurements of carbonation depth are performed according to BS EN 13295:2004 "Products and systems for the protection and repair of concrete structures - Test methods - Determination of resistance to carbonation" and BS EN 14630:2006 "Products and systems for the protection and repair of concrete structures - Test methods - Determination of carbonation depth in hardened concrete by the phenolphthalein method".
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14. Materials 1 : 3 : 0.5 Coatings Inhibitor standard proportions
cement : sand : water
Cement
CEM ΙΙ 32.5
Quarry sand
Coatings
1 : 3 : 0.5
Water
Inhibitor
Reinforcement B500C
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15. Chemical composition of Portland cement (%wt)
SiO2
Al2O3
Fe2O3
CaO
MgO
K2O
Na2O
SO3
CaO(f)
LOI
CEM II 32.5
20.67
4.99
3.18
63.60
2.73
0.37
0.29
2.41
2.52
Chemical composition of steel (%wt) C Mn S P Si Ni Cr Cu V Mo
0.22
1.24
0.044
0.032
0.28
0.09
0.10
0.52
0.075
0.028
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16. Organic Coatings Categories
Two-pack epoxy coating (E)
Two-pack polyurethane coating (P)
Nanotechnology coating (N)
Acrylic emulsion (A)
Elastomeric acrylic dispersion (R)
Uncoated specimens were used as reference (O)
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17. Coating procedure
The coating procedure for all coatings involves three layers:
The appropriate for each coating primer is applied on the dried surface of the specimen, to achieve the best adhesion between coating and mortar.
24 hours
The first layer of the organic coating is applied by brush.
The second layer of the organic coating is applied by brush perpendicularly to the first one.
Coated mortar specimens are stored in the laboratory for at least 7 days, so as coatings are dried and all quantity of solvents has evaporated.
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18. Organic coatings - technical characteristics
S/N
Code
Product
Color
Characteristics 1 Ε
Epoxy
Grey
Two-pack epoxy paint with amine hardener, density 1,55 kg/Lt, spreading rate 6 m²/kg (100 μm), solids 95% w/v. 2 P
Polyurethane
Two-pack polyurethane with aliphatic isocyanic hardener, density 1,20-1,40 kg/Lt, spreading rate 9-11 m²/ Lt (50μm). 3 N
Paint for exterior use
White
Siloxane paint, density 1,60 kg/Lt, solids 50% w/v, spreading rate 8,6 m²/Lt. 4 A
Acrylic emulsion paint for exterior use
Acrylic dispersion, density 1.46±0.05 g/ml, solids 61±2.5% w/w, pH 8.4±1, spreading rate 9±1 m²/Lt (2 coats). 5 R
Elastomeric insulating acrylic paint
Acrylic dispersion, undiluted for final coat, density 1.35 g/ml, solids 60±2% w/w, spreading rate 2±1 m²/Lt.
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19. Primers – technical characteristics
S/N
Code
Product
Color
Characteristics 1 ΕΑ
Epoxy primer (coatings 1-2)
Colorless
Two-pack epoxy primer, Α:Β-2:1 w/v with hardener, solids 58% w/v, density 0,99 kg/Lt, spreading rate 10 m²/Lt. 2 ΑΑ
Acrylic water-based primer (coating 3)
Density 1kg/Lt, solids 25,9% w/v, dilution up to 1:4 with water, spreading rate 8-32 m²/Lt. 3 SΑ
Styrene-acrylic primer (coatings 4-5)
Copolymers of styrene and acrylic resins, density 0.85 g/ml, solids 26±2% w/w, spreading rate m²/Lt.
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20. Conclusions A: Corrosion evaluation
The protective action of all organic coatings against corrosion of the embedded reinforcement is confirmed.
Epoxy and polyurethane coatings present an exceptional performance.
The nanotechnology coating presents reduced protective ability in accelerated corrosion conditions.
For the system “corrosion inhibitor – organic coating” the results have shown that their action is not added. However there is an improvement of the protection given by the coatings with the inhibitor presence, especially in the case of the less effective coatings.
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21. Conclusions B: UV radiation & Water/Water vapor permeabilities
Polyurethane coatings present excellent resistance to ultra violet radiation as compared to epoxy coatings that suffer from yellowing. Both coatings present very low water vapor transmission rate and liquid water permeability.
Radiation causes mild degradation to the acrylic and elastomeric emulsions. Both coatings present fairly good behavior towards moisture.
The nanotechnology coating resists very well to radiation and presents an improved behavior compared to all other coatings systems regarding water vapor transmission rate and liquid water permeability.
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22. Conclusions C: Carbonation
The two-component industrial coatings with organic solvent (epoxy and polyurethane coatings) provide the best protection.
Aqueous dispersions conventional coatings (elastomeric and acrylic dispersions) offer a satisfying level of protection.
The nanotechnology coating provides a low and negligible protection rate.
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23. Acknowledgements
This research has been co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: ARCHIMEDES III. Investing in knowledge society through the European Social Fund.
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24. Thank you for your attention!
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