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The resistance of rebars with functionally graded inorganic coatings against sodium chloride corrosion as is measured by impedance spectroscopy



Title: The resistance of rebars with functionally graded inorganic coatings against sodium chloride corrosion as is measured by impedance spectroscopy
Author(s): David Jolivet, David Bonen, Surendra P. Shah
Paper category : conference
Book title: International RILEM Symposium on Concrete Science and Engineering: A Tribute to Arnon Bentur
Editor(s): J. Weiss, K. Kovler, J. Marchand, and S. Mindess
Print-ISBN: None
e-ISBN: 2912143926
Publisher: RILEM Publications SARL
Publication year: 2004
Nb references: 23
Language: English


Abstract: The corrosion of reinforcing steel in concrete is considered a leading cause of premature deterioration of concrete structures. Apart from the incorporation of chemical corrosion inhibitors, the two main techniques that have gained a wide acceptance are cathodic protection and the use of epoxy coated reinforcing steel. The downsides are that the maintenance cost of the former is relatively expensive and the latter is susceptible to mechanical damage. In order to evaluate the corrosion resistance of inorganic coatings, sets of dowels coated with silicon powder, amorphous silica, slag and combinations thereof were prepared. The coating, with a total thickness of approximately 175 to 200µm, consists of an outer layer applied by plasma gun that overlays a nickel-chromium-boron (NiCrB) sub-layer in direct contact with the steel. The resistance of the coating against chemical attack and chloride-induced corrosion is evaluated by impedance spectroscopy measurements of the rebars immersed in simulated cement paste pore solution and the same solution containing 3.5% NaCl. The ionic strength of the solution is about 0.4 that is made of K+, Na+, Ca2+, SO4 ^2- and OH- at pH~13.4. Results suggest that the corrosion resistance increases in the order of plain rebar, plain rebar + inorganic coating, plain rebar + NiCrB sub-layer + inorganic coating. The best performance is achieved with a combination of silica powder and slag or simply silica powder. Interpretation of the results suggests that particle packing that forms an impervious barrier against aggressive ions ingress and the presence of a double layer structure are the key factors for preventing corrosion.


Online publication: 2004-03-25
Classification: Corrosion
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2912143926.057