Investigation of the anticorrosive effect of organic coatings on concrete reinforcement in the presence or absence of corrosion inhibitor by the Strain Gauge technique P.Pantazopoulou 1, S.Kalogeropoulou 1, A.Routoulas 1, D.Tseles 2 Technological Educational Institute of Piraeus, 1 Physics, Chemistry & Materials Technology Department 2 Automation Department eRA – 8, Piraeus, Greece, September 2013

Aim of the study This paper refers to the investigation of the action of organic coatings and corrosion inhibitor in the protection of steel reinforcement in highly corrosive conditions. Reinforced mortar specimens were coated with five different organic protective coatings: a two-pack epoxy paint, a two-pack polyurethane paint, a nanotechnology paint and two acrylic dispersions. The results of the applied methodology were encouraging for the fast monitoring and the classification of the protective action of the organic coatings against corrosion. eRA-82

Reinforcement corrosion – Protection measures Reinforcement corrosion: basic cause of reduction of a structure’s life  epoxy-coated reinforcement  stainless steel reinforcement  coating reinforcement  cathodic protection  paints on the surface of the concrete  corrosion inhibitors eRA-83 available protection measures

Organic coatings The use of organic coatings on the surface of reinforced concrete is the most widespread protective method, especially when long-term durability and superior performance are extremely significant. Coatings prevent the access of harmful substances for both the concrete and the embedded steel from the environment into the concrete, such as chloride ions, carbon dioxide or sulphur dioxide. 4eRA-8

Properties of organic coatings eRA-85  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.

Corrosion inhibitors Corrosion inhibitors have been successfully used as admixtures to concrete to reduce the risk of reinforcement corrosion. Alkanolamine-based corrosion inhibitors can make use of the porosity of concrete, by moving through the pore structure of concrete to reach the surface of reinforcing steel, where they form a protective film. They reduce chloride ion ingress into concrete. They are classified as mixed inhibitors, because they influence both the cathodic and the anodic process of corrosion. eRA-86

Investigation methodology  Corrosion measurement with the Strain Gauge (SG) technique. This technique, used for the fast evaluation of corrosive behavior of reinforcement caused under impressed anodic potential, is based on the appearance of swelling strain near the steel reinforcement in the concrete. The cause of the swelling tension is the formation of corrosion products (iron oxides, Fe 3 O 4, Fe 2 O 3, 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. 7eRA-8

Materials Quarry sand Coatings Cement CEM ΙΙ 32.5 Water Reinforcement B500C 1 : 3 : 0.5 standard proportions cement : sand : water 8eRA-8 Inhibitor

Chemical composition of Portland cement (%wt) eRA-89 SiO 2 Al 2 O 3 Fe 2 O 3 CaOMgOK2OK2ONa 2 OSO 3 CaO (f) LOI CEM II Chemical composition of steel (%wt) CMnSPSiNiCrCuVMo

Coatings categories  Two-pack epoxy coating  Two-pack polyurethane coating  Nanotechnology coating  Acrylic dispersion 1  Acrylic dispersion 2  Uncoated specimens were used as reference 10eRA-8

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.  24 hours  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. 11eRA-8

S/NCodeProductColorCharacteristics 1ΕEpoxyGreyTwo-pack epoxy paint with amine hardener, density 1,55 kg/Lt, spreading rate 6 m²/kg (100 μm), solids 95% w/v. 2PPolyurethaneGreyTwo-pack polyurethane with aliphatic isocyanic hardener, density 1,20-1,40 kg/Lt, spreading rate 9-11 m²/ Lt (50μm). 3NPaint for exterior use WhiteSiloxane paint, density 1,60 kg/Lt, solids 50% w/v, spreading rate 8,6 m²/Lt. 4AAcrylic emulsion paint for exterior use WhiteAcrylic 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). 5RElastomeric insulating acrylic paint WhiteAcrylic dispersion, undiluted for final coat, density 1.35 g/ml, solids 60±2% w/w, spreading rate 2±1 m²/Lt. eRA-812 Categories of organic coatings - technical characteristics

S/NCodeProductColorCharacteristics 1ΕΑ 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. 2ΑΑ Acrylic water- based primer (coating 3) Colorless Density 1kg/Lt, solids 25,9% w/v, dilution up to 1:4 with water, spreading rate 8-32 m²/Lt. 3SΑSΑStyrene-acrylic primer (coatings 4-5) ColorlessCopolymers of styrene and acrylic resins, density 0.85 g/ml, solids 26±2% w/w, spreading rate m²/Lt. eRA-813 Categories of primers – technical characteristics

SG specimens S/NCategoryInhibitorPrimerCoating 1SGE-EPE 2SGP-EPP 3SGN-AAN 4SGA-SΑSΑA 5SGR-SΑSΑR 6SGO--- 7SGN-AAAΑAΑN 8SGA-AASΑSΑA 9SGR-AASΑSΑR 14eRA-8

Shape and dimensions of Strain Gauge specimens (mm) 15eRA-8

Schematic diagram of corrosion test set-up 16eRA-8

SG values vs. time for all specimens eRA-817

Anodic current values for all SG specimens eRA-818

Mass losses of steel reinforcement in SG specimens eRA-819

Protection offered (%) eRA-820 Protection offered : [(ML U.S. – ΜL C.S. ) / ML U.S. ]. 100 Classification SGP – SGE > SGA > SGR > SGN

SG values vs. time for specimens with corrosion inhibitor eRA-821

Mass losses of steel reinforcement in SG specimens with corrosion inhibitor eRA-822

Conclusions 1 The measurements performed in this study verify the protective action of all organic coatings against corrosion of the embedded reinforcement, whereas epoxy and polyurethane coatings present an exceptional performance. The coating with the nanotechnology characteristics presents reduced protective ability, which can be attributed to the very slow action of its components compared to the rate of the implied corrosion. eRA-823

Conclusions 2 The results of the total corrosion protection of the system corrosion inhibitor – organic coating insinuates that their action is not added, but there is a selective improvement of the protection given by the coatings, especially in the cases when this protection is comparatively lower. eRA-824

SG specimens eRA-825

Laboratory corrosion test set-up eRA-826

Laboratory SG corrosion control system eRA-827

Cracked specimen eRA-828

Steel reinforcement eRA-829

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. eRA-830

Thank you for your attention! 31eRA-8