Is it possible to use 20% sodium hydroxide solution and 20% sodium hypochlorite solution for internal protection in vinyl resin fiberglass?
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Initially, a 20% sodium hydroxide solution is prepared and stored in a tank. When the chlorine pressure at the liquid chlorine station becomes too high, this sodium hydroxide solution is pumped out of the tank using a pump; it then passes through a transfer unit that absorbs the chlorine. During this process, HCl, NaCl, and NaClO are formed, after which the solution is circulated back to the tank for storage, until its concentration drops to around 5%. At that point, the solution is taken out, and the sodium chloride and sodium hypochlorite contained in it are removed. Afterwards, sodium hydroxide is added again to bring the concentration back above 20%, after which the solution is once more circulated back to the tank for storage. Through analysis of this process, the liquid medium in the tank, which is a 20% sodium hydroxide solution, gradually transforms into a 5% sodium hydroxide solution as well as a 20% sodium chloride and sodium hypochlorite solution, with the temperature remaining around 60 degrees Celsius. Now, the client requests that fiberglass-reinforced plastic be used for anti-corrosion protection of this tank, as concrete walls simply cannot withstand strong alkaline corrosion and get damaged within just one month. Previously, our company used fiberglass-reinforced plastic made from epoxy resin modified with furan for internal anti-corrosion protection in such tanks, but even in that case, the fiberglass was completely corroded in less than half a year. I spent many days searching for information online, and it seems that fiberglass made from vinyl resin should be able to resist corrosion from such media for at least one to two years. However, the application of vinyl resin is complicated, mainly due to issues related to adhesion; I’m worried that after installation, it might separate from the wall over time, which would be a huge embarrassment. Are there any experts in this field online who could offer some advice? It seems that there are very few people working with fiberglass these days. . .
You can consider using a resin on the inner layer and applying a layer of vinyl resin on the outside!
We have encountered such problems in thermal power plants; we use the British polymer material Veilcoat coating for protection. The effect is pretty good. For several years now, there have been no problems.
FRP materials may not be able to withstand such high concentrations of NaOH; other reinforcement methods could be considered. The base layer can use an epoxy leveling compound, while the top layer can use vinyl; this way there will be no problems
For the corrosion protection of concrete surfaces, it is essential to properly handle the sealing and anti-seepage measures for the substrate; a corrosion protection plan based on the substrate is the preferred approach.
Choosing polyaniline is no problem – it offers a good cost-performance ratio and excellent performance
Liquid caustic at 60 degrees Celsius poses no major problem for vinyl resin, but the glass fibers used for reinforcement are glass filaments that cannot withstand strong alkalis.