In the container coating process, "pre-spraying" is an important . At present, many container owners and inspectors have strengthened the inspection of the coating quality of the pre-sprayed parts. According to the established process flow, the box welds need to enter the pre-spraying station immediately after sandblasting.
1. Pre-sprayed parts
The pre-spraying parts mainly include the following three places.
(1) The steel on both sides of the weld seam is assembled by electric welding, resulting in uneven distribution of thermal stress in the steel structure and differences in internal electrode potentials, making the weld seam particularly prone to corrosion; in addition, in the sandblasting room of the weld seam, the The shop primer coating film is easy to rust if it is not pre-sprayed in time.
(2) The secondary corrosion part is in the sandblasting room, and the secondary corrosion part has been primer should be pre-sprayed immediately at the pre-spraying station.
( 3) "Dead corners" on the box structure As container coatings are all made of high-pressure airless spray paint, it is difficult to spray on many parts of the box structure, and pre-painting is required. The outer parts of the box mainly include door locks and hinge plates, etc.; the inside and outside of corner castings ; The "dead corners" and welds in the box and the bottom of the box, such as the welds of the front and rear lower beam reinforcement plates, the inner sides of the corner columns, the slopes of the end plates on the side of the left and right corner columns, and the back of the welds of the solid parts , etc., all need to be pre-coated.
Second, the method of pre-spraying
The original Shanghai Huahai Container Manufacturing Co., Ltd. used the method of pre-coating and then pre-spraying on the welds of the box to ensure the film thickness. For other parts, use the method of brushing before spraying large areas. Although brushing is a simple manual coating method, according to the structural characteristics of the container, brushing is done with a 2. Sin (6. 35cm) wide curved handle paintbrush, which is flexible and convenient to operate, and can be used where the paint tool is difficult to spray . Brushing to the parts, brushing also has strong penetration, which can make the paint penetrate into the pores and crevices. And when there is a small amount of moisture on the surface to be painted, brushing can drive out the water, so that the paint can adhere to the surface better. Another advantage of brushing is that there is less paint waste and less environmental pollution. For the pre-coating of the large flat parts of the upper and lower parts of the container, the stick coating method is generally used in production, and the effect is also good. Rolling is more efficient than brushing.
3. Pre-sprayed materials
In order to ensure the anti-rust quality of welding seams and pre-painted parts, epoxy zinc-rich primer is required for pre-spraying , and the dilution rate of pre-spraying paint is 15% to increase the penetration of epoxy zinc-rich primer and make it easy to operate.
Some box factories have set up a pre-spraying station for asphalt paint at the bottom of the box before the topcoat drying room to prevent the bottom beams, end sills, and thresholds from being sprayed with asphalt after the floor is covered, which will affect the coating quality. Most box factories need to pre-coat topcoat on the chain (seat) plate, lock lever sheath and other parts.
