Research on guarantee measures for steel drum coating quality (3)

Research on guarantee measures for steel drum coating quality (3)

Fifth, the requirements of the steel drum painting process

In order to ensure the quality of the steel drum coating, it is necessary to consider not only the quality of the surface of the steel drum, but also the use, performance and construction process of the coating itself, because the performance and function of the coating are reflected by the coating. Therefore, the choice of coating variety, suitable coating process and coating equipment and working environment are mutually reinforcing and mutually restrictive. To this end, the following points must be understood when painting steel drums:

(1) Formulating a reasonable steel drum painting process

According to the specific use of the steel drum and the quality requirements of the coating, as well as the actual situation of each steel drum manufacturer, a scientific, advanced and reasonable coating process is formulated. The content should include: paint variety, detailed painting process and technical conditions, equipment and tool quality standards and testing, acceptance criteria and methods, etc., in order to facilitate the operator to select the paint type according to the process requirements, and finely operate according to the process requirements. In order to ensure the surface quality of the steel drum.

(2) Strictly carry out the treatment before the surface of the steel drum is painted

Steel drums are exposed to air during the production, storage, transportation and production of raw materials. Corrosion is easy to occur due to the action of oxygen and water in the air and possibly sulfur dioxide, carbon dioxide, hydrogen sulfide, etc., followed by the transportation of raw materials and steel drums. In the process, it is easy to adhere to foreign matter, such as oxide scale, oil stain, processing debris, dust, etc. Third, most manufacturers use tin welding for repair welding of leaking steel drums, because hydrochloric acid is used before soldering. The surface of the welded surface is corroded, and the chlorination of hydrochloric acid in the hydrochloric acid diffuses in the surrounding air, which is also likely to cause corrosion of the metal on the surface of the steel drum. As a result, the performance of the steel drum is reduced or even damaged. Therefore, the surface treatment must be carried out before the steel drum is coated to eliminate the unfavorable factors affecting the quality of the steel drum coating, thereby improving the coating quality of the steel drum, which is very important for the steel drum.

(3) to ensure the drying of the surface coating of the steel drum

The coating is applied to the surface of the steel drum, and most of it is a process from liquid to solid film (except powder coating), which is called the dry film formation process of the coating. The dry film formation process is a comprehensive physical-chemical process including solvent evaporation, condensation, oxidative polymerization, etc. The whole process has both physical and chemical effects, which can be roughly divided into two stages:

1. Solvent evaporation stage

The solvent volatilization stage on the steel drum generally occurs in the early stage of drying, and immediately after the coating, a large amount of solvent is volatilized, and the volatilization process is carried out almost on the free surface of the liquid. Due to the volatilization of the solvent, the concentration of the coating film changes, causing the coating to lose fluidity.

2. Chemical reaction stage

In the steel drum, the solvent volatilizes and loses the fluidity. Under the action of thermal energy, there are some polymer compounds which form a network structure by condensation reaction; other paint bases are oxidized in the air, and the polymerization reaction is carried out to form a high network structure. Molecular compound. This process is a relatively complicated chemical reaction process, but the final generation is a polymer compound having a network structure with different degrees of polymerization. The high-performance polymer compound has good performance, and almost all the protective properties of the coating film are provided by it.

In summary, it is known that heat and time are essential in the dry film formation process. Without sufficient heat and sufficient time, the coating will not get enough chemical reaction energy or the reaction will not proceed completely. The so-called selection of appropriate drying specifications is to set a reasonable matching of drying temperature and drying time in order to obtain sufficient heat, so that the coating film can reach the optimal structure for protecting steel drums and decorative steel drums.

(4) Strictly monitor the coating quality of steel drums

In order to ensure the coating quality of the steel drum and prevent the repair of a large number of steel drums, it is necessary to have accurate testing instruments and reliable testing methods to monitor every important part of the steel drum painting operation to control the quality of the steel drum coating. The high standards set. The inspection of the quality of the steel drum coating includes the detection of the quality of the pre-painting treatment, the inspection of the quality of the coating product itself, the quality monitoring of each process in the coating construction process, and the detection of the quality of the coating film after the coating is completed.

The quality inspection of steel drum coating can be divided into surface quality inspection, intermediate inspection and final inspection before spraying.

The surface quality of the steel drum before painting is the basis of the coating, which directly affects the coating quality of the steel drum. The main contents of the inspection are as follows:

1. Detect the concentration of the surface treatment agent of the steel drum before painting, the liquid temperature, the cleanliness of the washing water, and the injection amount of the nozzle.

2. Check the surface condition of the steel drum after treatment. The surface of the steel drum should be free of grease, dirt and other residues. If chemical treatment is used, the film should be uniform, dense and rust-free.

The intermediate test includes the quality inspection of the process such as moisture and spraying. The main contents are as follows:

1. Check if the moisture is completely removed before spraying, including whether there is residual water in the steel drum.

2. Detect the quality of the coating used for spraying, including whether the viscosity and other indicators meet the requirements.

3. Detect the quality of the spray, and there should be no serious defects such as sag and exposed bottom after the spray leveling.

The final test refers to the quality inspection of the finished product after the steel drum is painted and dried. The main contents are as follows:

1. Detect the quality of the coating film. The coating film should not have defects such as particles, biting, pinholes, etc.

2. Detect the dryness, hardness, thickness and adhesion of the coating film. The coating film should be completely dry, the coating film thickness is uniform and the process requirements are met, and the hardness and adhesion of the coating film should also meet the required standards.