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

Abstract

Organic-inorganic hybrid (OIH) matrices were synthesized by sol-gel method and deposited on hot-dip galvanized steel (HDGS) using a dip-coating process. These OIHs, generally called amino-alcohol-silicates, were synthesized using a functionalized siloxane, 3-glycidoxypropyltrimethoxysilane, and five oligopolymers (Jeffamine) with different molecular weights: 230, 400, 600, 900 and 2000. Besides the five different pure OIH matrix coatings, a similar set of HDGS samples were coated with the OIH matrices doped with Cr(III), which was tested as a corrosion inhibitor. The OIH coatings were assessed using electrochemical studies, namely electrochemical impedance spectroscopy, macrocell current density, open circuit potential monitoring and polarization resistance. The studies were carried out in mortar. Analysis of the results obtained by optical and scanning electronic microscopy methods were consistent with the data obtained by electrochemical techniques. The HDGS samples coated with OIH matrices showed better performance when compared with HDGS uncoated samples. During the last three decades, the corrosion of steel reinforcement has been widely studied and reported. [1][2][3][4][5][6][7] In spite of the majority of the reinforced concrete (RC) structures showing high durability, serviceability and long-term performance as well as intense research being performed in the last few years, a large number of failures have been reported due to the corrosion of the reinforcement embedded in the concrete.The most effective way to minimize the risk of corrosion reinforcement concrete is to ensure that the cover of the metallic reinforcement parts is of an adequate thickness. The concrete should be of high quality, with a proper mixing ratio, good compaction and curing. 1,6,7 Several proven methods are known for preventing and controlling corrosion. Improving the concrete quality and increasing the concrete cover are the most economical protection measures yet are not always enough. A method that is widely accepted and recognized as efficient at providing corrosion protection of the RC structures is the application of hot-dip galvanized steel (HDGS), since it is considered economically favorable when compared to others. The use of HDGS has been recognized by several authors 7,[8][9][10][11][12] as an effective measure to increase the service life of RC structures exposed to carbonation or to chloride ions. However, zinc in contact with fresh concrete (high alkaline environment) is oxidized and hydrogen evolution occurs, for a limited period, until passivating formation layers occur and concrete hardens. To avoid zinc corrosion and hydrogen evolution, chromate and similar hexavalent chromium compounds are among the most common substances used as inhibitors or incorporated into the preparation of the fresh concrete. However, these compounds are toxic and carcinogenic, causing serious environmental hazards and their incorporation in protective coatings is heavily regulated by most environmental legislation. Therefore, intense re...

Hybrid Sol-Gel Coatings: Smart and Green Materials for Corrosion Mitigation

“…In many instances, a dry gel needs further thermal treatment to be densified [20]. The sol-gel process versatility allows incorporation of additional components that introduce material's complementary functionalities, such as UV protection [21,22], anti-fouling [23,24], anti-reflection [25][26][27][28][29], moisture resistance [29][30][31][32][33], corrosion and adhesion protection [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53], along with the enhancement of mechanical, thermal, and optical properties, opening a wide range of application in several fields of science. Furthermore, this method allows the control of several experimental conditions leading to a simple sequence that may be tuned to the nature, final shape, and desired function.…”

“…Organic inhibitors derived from thiazole [103,107,122,129] have also shown quite good results. However, it has been reported that the presence of inhibitors within the sol-gel coating, namely, when freely dispersed in the hybrid matrix, above a certain limit, has a detrimental effect in the long-term chemical stability and barrier properties of the coatings [43,44,121]. Consequently, several research efforts in this field have been focused on the development of micro-and nanocontainers compatible with hybrid sol-gel coatings that can be used for the controlled storage and release of the corrosion inhibitor ( Figure 9) [39,40,[130][131][132][133][134][135][136][137][138][139][140][141].…”

Hybrid sol–gel coatings for corrosion protection of hot-dip galvanized steel in alkaline medium

“…These OIHs, generally called ureasilicates [29] U(X) and amino-alcohol-silicates [30] A(X) were obtained using two different functionalised siloxanes: 3-Isocyanatopropyltriethoxysilane and 3-Glycidoxypropyltrimethoxysilane. Each functionalised siloxane was made to react with five oligopolymers (referred to as Jeffamine) with different molecular weights (MWs): 230, 400, 600, 900 and 2000.…”

Corrosion Protection Systems and Fatigue Corrosion in Offshore Wind Structures: Current Status and Future Perspectives

“…In the last decades, EIS has been widely used for coatings characterization [119,120,[193][194][195][196][197][198][199][200][201][202]. EIS is a transient technique where a sinusoidal signal (potential) is applied with low amplitude, to not disturb the equilibrium conditions of the system.…”

“…In the last few decades, several types of organic-based coatings have been developed [85], including anti-fouling paints [70,[86][87][88][89][90][91][92][93][94], composites and nano-coatings [94][95][96], self-healing coatings [97][98][99][100][101][102][103][104][105][106][107], and hybrid sol-gel materials [98,[108][109][110][111][112][113][114][115][116][117][118][119][120][121] among others. However, as far as the authors' knowledge, very few studies were performed on OWSs using self-healing and hybrid sol-gel coatings.…”