Why is the corrosion on the upper and lower parts of the outer wall of a light oil tank different?
Thread Content
The anti-corrosion coating on the outer wall of the oil tank in the image was applied at the same time, using the same coating and the same application process. Why are the results different, with more corrosion in the upper part than in the lower part?
As can be seen from the images, the corrosion in the areas below the wind resistance ring and below the rain guards over 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 take into account these different areas – the upper part of the tank, 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 layers.
From a visual perspective, how can the design structure be improved?
It seems that the rustwater resulting from corrosion at the edge of the tank roof, or at the junction where the tank roof railing meets the tank roof, has contaminated the upper part of the tank wall surrounding the wind-resistant ring. The rustwater flowed away along the outer edge of the I-beam forming the wind-resistant ring, so it did not contaminate the lower part of the tank wall. The lower edge of the tank wall vent hole is not covered by rust water either, as it is blocked by the vent hole cover.
Only this 1 tank is like this; it is not the result of normal external atmospheric corrosion! Guess 1: After the gaseous medium in the tank overflowed from the top of the tank, it happened to rain, leading to corrosion. 2. If the tank is not used for a long time but the medium inside remains, water will condense on the upper part or the tank top, and as it flows down, it causes corrosion! Recommendation: keep warm!
Volatile recovery by nitrogen sealing or water seal tank installation
Agreeing with your view, based on the images, it seems that the construction of the tank’s roof was inadequate, or large amounts of corrosive gases were escaping from areas such as the vent holes on the roof, resulting in severe corrosion of the roof. As rainwater flows down the outer wall of the tank, the wind-resistant ring prevents communication between the upper and lower parts of the tank
Currently, nitrogen sealing is the most common option, as it is safe and environmentally friendly.
It seems more like it’s caused by an insufficient number of anti-corrosion layers during the application of the upper anti-corrosion coating; measuring the thickness of the coating will make it clear