Corrosion Protection of Hot Dip Galvanized Steel in Mortar

Abstract

Corrosion of steel in concrete is one of the major causes of structure degradation, requiring expensive maintenance. The using of hot dip galvanized steel (HDGS) has been recognized as one effective measure to increase the service life of reinforced concrete structures in marine environmental. However, HDGS corrodes in contact with high alkaline environment of fresh concrete. Although this initial corrosion process allows the formation of a protecting layer barrier, the corrosion that occurs initially is harmful and chromate conversion layers are usually used to prevent it. Due to toxicity of Cr(VI), these kinds of pre-treatments have been forbidden and hybrid coatings have been proposed as alternatives [1][2][3]. To evaluate the performance of these coatings, beyond the laboratory characterization, in situ tests in real conditions should be performed. An electrochemical system to measure the macrocell current density (i gal ) was designed to evaluate the degradation of HDGS coated samples with different organic-inorganic hybrid films, embedded in mortar during 70 days, using an automatic data acquisition system. This system revealed to be feasible and highly sensitive to coatings degradation. Also, allow distinguishing different hybrid coatings with different thicknesses.

Alcohol-Aminosilicate Hybrid Coatings for Corrosion Protection of Galvanized Steel in Mortar

“…The edges of both CE and WE plates, as well the non-active areas and connecting zones were protected with a dual-component epoxy resin (Araldite) using a previously established protocol. [27][28][29] For comparison purposes, cells prepared with non-coated HDGS WE electrodes were used as control. To assemble the electrochemical cells, 120 ± 10 g of fresh mortar was transferred to a 100 mL polyethylene flask, the electrodes were subsequently immersed and the flask closed.…”

“…27 A titanium-activated wire with a length of one cm was used as a reference electrode (RE) and a HDGS plate with an active area of 2 cm 2 coated with OIH was used as a working electrode (WE). The electrodes were connected to an isolated copper cable and the cutting zone of the tip of the titanium electrode was covered with dual-component epoxy resin (Araldite).…”

Ureasilicate Hybrid Coatings for Corrosion Protection of Galvanized Steel in Chloride-Contaminated Simulated Concrete Pore Solution

“…The results also indicated that the i gal cells in SCPS were sensitive to the external laboratory temperature variation, to the presence of chloride ions and to the composition of the OIH material deposited which is also according to the literature. 44,46 Polarization resistance (R p ).- Figure 11 shows the R p values obtained for the different electrochemical cells prepared with HDGS coated by one dip step (1 layer), that were immersed in SCPS during 16 days. Results for control samples are also presented.…”

“…27,44 For comparison purposes, cells prepared with uncoated HDGS WE electrodes were used as control and triplicate cells were assembled to check data reproducibility. To assemble the electrochemical cells, the SCPS was transferred to a 100 mL polyethylene flask.…”

“…7,[42][43][44][45] i gal measurements allowed for real-time and continuous monitoring, providing semi-quantitative information about the corrosion rate and detected the instant where the construction steel depassivates. 44,46 The R p measurements were performed periodically since these allowed for measurement of instantaneous corrosion current density in order to assess the condition of the embedded steel reinforcement related to its corrosion. 47 EIS is a reliable, non-destructive and fast method providing accurate results about corrosion protection behavior of the OIH sol-gel coatings.…”