Why is the corrosion on the outer wall of the naphtha tank different between the upper and lower sections?
Thread Content
As can be seen from the images, the corrosion in the areas below the wind resistance ring and below the rain guards of the breathing holes is relatively mild compared to other areas; this indicates that the most severely corroded areas are those subjected to interfacial corrosion between the gas and liquid phases, as well as corrosion caused by acidic substances originating from the tank top and moving downward. Due to the protective effect of the wind resistance ring, the corrosion on the lower parts of the tank wall is more severe. Therefore, when designing oil tanks with wind resistance rings for corrosion protection, it is necessary to tailor the design to different areas – the upper part, the tank top, and the upper attachments should be designed and constructed with enhanced corrosion protection measures, including an increased thickness of the protective coating.
The different corrosion patterns in the upper and lower halves of the outer wall of the naphtha tank are mainly due to the boundary between the gas phase and the liquid phase, as well as the formation of open acid mist, which leads to more severe corrosion in the upper area above the tank roof and its vicinity. Furthermore, the presence of the wind-resistant ring blocks some corrosive agents, resulting in relatively less corrosion at the lower part of the tank. Therefore, during design and construction, different anti-corrosion measures should be adopted for various parts; in particular, the upper section and the tank top require enhanced anti-corrosion treatment as well as an increased thickness of the anti-corrosion layer. .
What if there is an external angle steel ring at the tank wall and the tank top?