Available online at www.CivileJournal.org Civil Engineering Journal (E-ISSN: 2476-3055; ISSN: 2676-6957) Vol. 9, No. 12, December, 2023 2970 Effect of Silane and Silicate based Penetrants against Corrosion of Steel with Partial Cover Thickness Muhammad Afaq Khalid 1* , Shinichi Miyazato 1 , Tatsuya Minato 1 , Hibiki Mizuguchi 1 1 Department of Environmental and Civil Engineering, Kanazawa Institute of Technology, Nonoichi 921-8501, Japan. Received 20 August 2023; Revised 22 November 2023; Accepted 27 November 2023; Published 01 December 2023 Abstract The partial cover thickness of reinforced concrete structures near the coastline enhances the early corrosion onset, which reduces the service life. As a countermeasure under the preventive maintenance approach, to delay early corrosion onset in structures with partial cover thickness and increase durability throughout the service life, this study used silane and silicate-based surface penetrants. Mortar specimens with a partial cover thickness and embedded, specially segmented bars were prepared. Both penetrants were applied to specimens with partial cover thicknesses (20 and 7.5 mm). Further, electrochemical methods such as macrocell current, microcell current, electric resistivity, and potentiodynamic polarization curves were used to assess the corrosion resistance before and after coating. The penetration depth of silane was measured visually, and the Vickers hardness test was used for the silicate penetrant. The “equivalent cover approach” was adopted to evaluate the performance of penetrants throughout their service lives. Results revealed that the total corrosion current density decreased by 79% for specimens coated with silane and 52% for silicate penetrant, whereas no change was observed in the uncoated specimens. Based on the equivalent cover approach, the silane penetrant was determined to be most effective in delaying the corrosion onset and propagation time for cover thicknesses of 60 and 50 mm at 100 m distance against 70 mm, and for 40 and 30 mm against 50 mm at 250 m from the coastline. Further, the silicate-based penetrant was only effective for a deficient cover thickness of 5 mm against the specified cover thicknesses at a distance of 100 and 250 m from the sea coast. Keywords: Cementitious Material; Corrosion Rate; Corrosion Onset; Silane Surface Penetrant; Silicate Surface Penetrant. 1. Introduction The concrete cover in Reinforced Concrete (RC) structures protects steel from external environmental effects, preserves passive film, and maintains the bar in a highly alkaline state. At the construction stage, if the specified cover thickness, including the allowable tolerances [1–3], is not achieved, a variable/partial cover thickness is constructed at different sections of the structural member. Owing to the porous matrix and variable thickness of the concrete cover, the chloride ions and moisture in marine and de-icing salts should penetrate non-uniformly. This non-uniform penetration of chloride ions at different cover thicknesses reaches the steel surface by destroying the passive film and initiating corrosion when the chloride ion concentration exceeds the threshold. This partial cover thickness induces early corrosion onset [4], and timely intervention is required to delay corrosion onset and maintain the structure throughout its service life. The durability of RC structures depends on the characteristics of the cover [5] and primarily on the thickness and strength of the materials used. Steel embedded in a less impervious and thicker cover requires a long time to corrode and, hence, a longer service life of the RC structure [6]. A thin passive film of iron oxide in a highly alkaline environment * Corresponding author: c7000029@planet.kanazawa-it.ac.jp http://dx.doi.org/10.28991/CEJ-2023-09-12-02 © 2023 by the authors. Licensee C.E.J, Tehran, Iran. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).