Common problems can be roughly divided into three types, they are uneven coating, preservative dropping, and preservative blistering.

(1) Uneven coating. The fundamental manifestation of this type of problem is that the preservative is unevenly distributed on the surface of the steel pipe, some parts are coated too thickly, and some parts are too thin or not applied to the oil at all. Therefore, the thickness of the coating in the place where the application is too thick exceeds the standard, resulting in waste; The place where it is painted too thin or not applied will cause the anti-corrosion ability of the steel pipe to decrease, resulting in the phenomenon of rust.

(2) Preservative hanging drops. The preservative solidifies on the surface of the steel pipe like water droplets is the phenomenon of preservative hanging drops, which often does not directly affect the anti-corrosion, and can also ensure the corrosion resistance required by the steel pipe; However, from an aesthetic point of view, the steel pipe with preservative hanging drops looks dull and uneven, which directly affects the appearance of the steel pipe.

(3) Preservative foaming. Due to the air entering the preservative, bubbles are formed in the steel pipe coating, and these bubbles are different in size according to the specifications of the steel pipe. The shape of the larger bubble is like the bubble on the protective cover of the remote control of some home appliances, and the hand will break the bubble when pressed a little harder. The blistering phenomenon of preservatives not only affects the appearance of the steel pipe, making the surface of the entire steel pipe appear rough and not smooth, but also the damage of the bubbles will reduce the standard of coating film thickness, reduce the anti-corrosion ability, and lead to rust of the steel pipe where the bubbles are located.