How to prevent corrosion of steel beams in sewage treatment tanks?
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Below is the steel beam of the cover plate for the petrochemical wastewater treatment tank; the anti-corrosion coating applied to it failed after less than 2 years. Let’s see if there are any effective anti-corrosion measures.
Corrosion protection for the steel beams in petrochemical wastewater tanks is indeed a challenging issue, especially since chemical wastewater is highly corrosive; it’s normal for ordinary coatings to fail after just two years. I suggest trying these methods: 1. **Proper surface treatment is essential**: The surface of the steel beams must be thoroughly rust-free; it’s best to achieve a Sa2.5 grade (almost white), with a roughness of 40–70 microns, so that the coating can adhere firmly. 2. **Coating system upgrade**: - The primer is epoxy zinc-rich or inorganic zinc-rich to provide cathodic protection ； - The intermediate coat uses epoxy ferrochrome to provide a thicker layer that prevents corrosion ； - The topcoat is made of polyurethane or fluorocarbon paint, resistant to chemical corrosion and ultraviolet rays. - The total dry film thickness should ideally be between 280–350 μm; in particularly harsh environments, it can be increased to over 400 μm. 3. **Consider a heavy-duty anti-corrosion solution**: - If the budget permits, a glass flake mortar coating can be used; it is highly resistant to acids and alkalis and can last 5–8 years without issues. - Or hot-dip aluminum/zinc coating with a sealing layer for long-term corrosion protection, lasting over 10 years. 4. **Regular inspection and maintenance**: Inspect the coating once a year, and repair any damage promptly to prevent minor issues from developing into severe corrosion. Combined, these measures should be able to significantly extend the service life of steel beams. If a more specific solution is needed, you can consult a professional anti-corrosion company to assess the site conditions. .
Your tank is an anaerobic or hypoxic/hydrolytic acidification tank; the main forms of corrosion are caused by hydrogen sulfide and water, as well as by high concentrations of hydrogen sulfide resulting from exhaust gas collection. It is recommended to apply epoxy coal tar paint three times – this approach yields good results in practice. Glass flake coatings are too expensive for this purpose.