Which parts of the metal columns need further improvement in terms of corrosion protection?
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The image below shows the metal supports in the pipe racks of a chemical plant. In our equipment management processes, we often fail to pay attention to details, which can lead to corrosion damage to both the equipment and the steel structures. Is there anything else that needs to be done regarding corrosion protection in that part of the diagram below?
The front side of such columns is relatively easy to handle; it just involves mechanical rust removal on the two bottoms and two sides. The tricky part is inside the pillar. Especially at the column pier areas, we seal every corner of those areas thoroughly with fire-resistant coating materials, both on the inside and outside. This approach will at least work for three years. :lol
The equipment operates at high temperatures, so heat-resistant paint is required. There are also coatings for fire and explosion prevention. All carbon steel areas must be fully painted; otherwise, pitting corrosion will initiate widespread cracking in the surrounding area.
Inadequate rust removal and insufficient thickness of the primer
In such a corrosive environment, the metal surface must first meet at least St3 level in terms of corrosion resistance; the anti-corrosion coating should be at least 200 microns thick, and a coating that is resistant to corrosion and atmospheric aging should be used. For the hollow part of the column, it can be sealed with concrete to prevent water from accumulating inside.
During the design phase, a box-type structure is adopted to prevent corrosion inside. At present, the columns are rusting; without replacing the steel structure, they have been completely covered with anti-corrosion materials to prevent further corrosion both on the inside and outside. Construction can be carried out with rust present, without affecting the anti-corrosion effect.
Each time, one just applies the paint according to the color; whether the surface is of type St, Sa, or something else, only the steel profiles know that. As a result, it’s impossible to determine whether it’s good or bad, whether there’s enough paint or not, or whether it meets the requirements. In any case, once the paint in the bucket runs out, the steel profiles change color – this is what most people do. I remember that in the past, painting by rural carpenters was a skillful task that not everyone could handle. Now, anyone can do it, but they’re reluctant to do so because it’s unpleasant and the paint stains clothes. So, to sum up, the key lies in the process of application: if rust is removed properly, the lifespan of the paint will be much longer. Generally, the quality of paint applied in manufacturing plants is far better than that used in on-site applications. I think there must be differences in the painting techniques used.