Problems of anti-corrosion coating materials on the surface of steel pipe

1. Role of coating materials

In order to prevent rusting, the outer surface of steel pipe is coated. Rust on the surface of steel pipe will affect the actual use effect, quality and appearance image. Therefore, the coating process of steel pipe has a great influence on the quality of steel pipe products.

2. Requirements of coating materials

According to the standards of the American Petroleum Institute, the steel pipe needs to remain corrosion-free for three months, so the anti-corrosion time of the steel pipe after coating needs to meet the requirements of this standard. However, nowadays, users have higher and higher requirements for the antirust time of the steel pipe, and many users require that the steel pipe can be stacked in the field for three to six months without rusting. In addition to the requirements for the antirust time, they also have certain requirements for the appearance quality of the coating, which is mainly reflected in the need for a smooth, clean surface after the coating of the steel pipe. The anticorrosive agent is evenly distributed on the surface of the steel pipe, no leakage, dripping phenomenon, does not affect the appearance quality.

3. Coating materials common problems

After summarizing, the common problems can be roughly divided into three types, namely, uneven coating, anticorrosive agent hanging drops and anticorrosive agent blistering.

(1) Uneven coating

The basic manifestation of this type of problem is the uneven distribution of the preservative on the surface of the steel pipe, with certain parts being too thick and certain parts being too thin or not coated with oil at all. As a result, the thickness of too thick a coating will exceed the standard, which leads to waste; too thin or uncoated coating will reduce the corrosion resistance of the steel pipe and lead to rust.

(2) Hanging drops of preservative

Anti-corrosion agent solidifies on the surface of the steel pipe like water droplets, which is the phenomenon of anti-corrosion dripping, and the occurrence of this phenomenon usually does not directly affect the corrosion resistance, and also ensures the required corrosion resistance of the steel pipe. But from an aesthetic point of view, steel pipe with anticorrosive agent hanging drops looks not smooth, uneven, directly affecting the appearance of the steel pipe.

(3) Preservative blistering

Due to the anticorrosive agent into the air, making the formation of air bubbles in the coating of the steel pipe, these bubbles have different sizes according to the specifications of the steel pipe. The shape of the larger bubbles is similar to the bubbles on the protective cover of the remote control of some household appliances, and pressing the bubbles by hand will cause them to rupture. The phenomenon of anticorrosive agent blistering not only affects the appearance of the steel pipe and makes the entire surface of the steel pipe appear rough and unsmooth, but also the destruction of the bubbles will reduce the standard of the coating film thickness, reduce the corrosion resistance, leading to corrosion of the steel pipe parts where the bubbles are located.