Optimization of silane sol–gel coatings for the protection of aluminium components of heat exchangers

Abstract

Despite the relatively low mechanical properties respect to the aluminium alloys but due to high thermal exchange capacity, pure aluminium (AA1XXX series) is widespread for industrial applications for heat exchanger components or cooling systems (like refrigerator systems). The corrosion protection properties of aluminium components are commonly enhanced by applying organic coatings or by performing chemical conversion treatments on aluminium surface. One of the routes for the protection of aluminium components for heat exchangers is the application of silane sol-gel coatings. In this work, a thin silane sol-gel coating improving the corrosion protection of aluminum for heat exchanger and avoiding the loss of thermal exchange due to the presence of the protective layer was developed. Prior to deposit, the silane layer as a mixture of three different silicon alkoxides precursors (such as tetraethoxysilane, glycidoxypropyltrimethoxysilane and methyltrithoxysilane), the optimum surface chemical treatment of the 1050 aluminum alloy, widely employed in the heat exchanger and cooling system industry, was investigated using electrochemical impedance spectroscopy (EIS). In order to enhance protective properties, different amounts of nano-sized sodium montmorillonite were embedded into the silane network. Through taking advantage of some parameters extracted from EIS, the most efficient concentration of nanoclay was determined, confirmed by scanning electron microscopy and Fourier transform infrared analysis as well. The resistance of the different sol-gel layers to thermal cycles (strictly related to the application in the heat exchanger industry) was carried out to stress the sol-gel coating. The behavior of the investigated sol-gel layer after the thermal cycles was evaluated by means of EIS.

Determination of Optimum Concentration of Benzimidazole Improving the Cathodic Disbonding Resistance of Epoxy Coating

“…The consequence of these contradictory issues was inferior and superior behavior of the epoxy coatings with one and 0.75 wt.% BIM, respectively. This was in agreement with the results of our previous works, where exceeding the optimum concentration of corrosion inhibitors adversely affected the coating performance [35,39]. In the case of organic inhibitors liberated from Mentha At the next step, different concentrations of benzimidazole (0 wt.%, 0.5 wt.%, 0.75 wt.%, and 1 wt.%) were introduced into the epoxy-polyamide coating formulation applied on ST37 substrate and cathodic disbonding test (−1.2 V vs. Ag/AgCl for 24 h) was conducted on the coated samples.…”

The influence of organophosphonic acid and conducting polymer on the adhesion and protection of epoxy coating on aluminium alloy

“…A wide amount of works concerning the anticorrosive performance of metals coated with sol-gel films obtained by silica precursors has been published [12][13][14].…”

Electron-optical and Auger electron spectroscopy studies of a zirconium conversion coating on aluminium

“…9,10 Though findings suggest that these replacements have a lower corrosion resistance compared to the chromate coatings, they display fairly good paint-adhesion characteristics. Other researchers [11][12][13][14][15] developed sol-gel coatings as alternatives to chromates with a limited success while the improvements in their corrosion performances were engineered with nano-containerization of the green corrosion inhibitors into the coating fabrics. [16][17][18][19][20] In order to avoid the contact of chromium compounds with foodstuffs, the canning industries have stringent policies with respect to chromates.…”