In this article, we will explain the importance of applying a good coating to manhole covers and manholes.
If a good anticorrosive coating is not applied to these, they could compromise road safety, and could lead to an accident, due to the catastrophic effects produced by the Corrosion as a result of the well-known "sewer gas".
He "Sewer gas" o Hydrogen sulfide is formed from a biological reaction in sewage systems through anaerobic fermentation (without oxygen) of organic matter present in wastewater.
Hydrogen sulfide is a colorless and harmful gas, as well as highly corrosive. In the humid and warm environments of the sewer network, the H2S oxidizes to sulfuric acid. This sulfuric acid is corrosive and attacks wastewater.
In fact, biogenic corrosion is driven by the biological activity of various "acidophilic" bacterial strains, that is, bacteria that need an acidic environment to thrive. A tiny Thiobacillus Thiooxidans biofilm can produce enough sulfuric acid to corrode up to 25mm of concrete in one year.
Therefore, if preventive measures are not taken, it will end up corroding any type of substrate exposed to said acid (steel, concrete, cast iron ...).
How can we extend the service life of manhole covers?
A few years ago, a renowned foundry contacted Cover to try to find a solution to this problem. Both Valencia City Councils and Alicante City Councils were suffering the devastating effects of this type of corrosion. This foundry carried out a test with different national coating companies to test different types of coating.
At Cover and for this, we opted for thermoplastic Plascoat PPA571 from the house Axalta to perform such tests. After a year exposed in the most aggressive areas of these cities, the results were benevolent for us, being the coating that gave the best results. The lining of the manhole covers remained intact as the day they were installed a year ago.
With PPA571, and after optimal surface preparation (degreasing and expulsion of gases from the substrate in a pyrolytic oven + abrasive blasting to SA 2.5 grade to achieve excellent adhesion) we manage to isolate the piece from any corrosive agent thanks to the so-called “barrier coating”. And it is called this way, since we give the piece a high thickness, creating a membrane that isolates the metallic substrate.
If you want to know more about this anticorrosive coating for manhole covers and sewers, do not hesitate to download the catalog with our main thermoplastic products.