Surface pre-treatment
If there are impurities, oil, grease and fouling on the surface, they should be removed in accordance with the cleaning method specified in SY/T0407 of the Code for Pretreatment of Steel Surface Before Coating.
The steel surface should be sprayed to remove rust according to the method specified in SY/T0407. When carrying out spraying operations, it should be carried out in the order of first top, then wall and bottom back. The rust removal quality should reach the Sa2.5 grade specified in GB/T8923-1998 "Corrosion grade and rust removal grade of steel surface before painting", and the anchor depth is selected according to the anti-corrosion grade, ordinary type: about 40μm. Choose 6-8mm nozzle, nozzle inlet compressed air pressure 0.5-0.6Mpa, spray angle 30-75°, incidence distance 100-200mm, sand particle size 0.8-4 mm. When sandblasting thin steel plate, the sand particle size and air pressure should be appropriately reduced, and the nozzle shall not continue to be used when the wear amount of the sandblasting outlet end and diameter exceeds 1/2 of the starting inner diameter. The surface pretreatment of the attachment should be the same as that of the main part.
After spraying, the surface should be purged clean with dry, clean, oil-free compressed air.
After spray derusting, defects exposed by the steel surface and welds must be treated.
Safety measures: keep ventilation so that the solvent gas concentration is below the dangerous concentration, spray workers wear protective clothing and masks, and clean up immediately after the spray pipe touches the nose with ground.
Paint formulation
If the anti-corrosion paint is a two-component coating, the two components can be mixed and formulated before application, and it is confirmed before preparation whether the A and B components are matched, whether they are consistent with the required application model, and whether they are invalid.
Before dispensing groups A and B, they must be stirred until the bottom is free of deposits and uniform up and down.
A small amount of test coating is prepared according to the proportion required by the manual, and the viscosity is adjusted with a special diluent to achieve the best coating process conditions and ensure the thickness and quality of the single film.
According to the coating area and the thickness of the single coating film, calculate the dosage of A and B components, and control the amount of ingredients to be used up within 6 hours to prevent too much dosing, overtime application and excessive curing and thickening of the coating affecting the quality of the coating film.
The amount of special thinners for coatings should be controlled to not exceed 15% (spraying) or 8% (brushing) of the total weight, adding components A to the calculated ratio and stirring evenly, and then adding components B to stir for 10-15 minutes to ripen components A and B, and finally standing for 15-20 minutes to eliminate the air bubbles introduced by stirring. The length of stirring and letting time depends on the amount of ingredients.
The mixed paint can be sprayed after filtering with a 100 mesh filter. Once the paint overreacts and thickens during the spraying process, stop spraying immediately. If the paint has been scrapped, it should be re-batched. The coating overreaction time is related to the ambient temperature, the time required for high temperature is short, and the material should be less matched, on the contrary, the low temperature takes a long time, and the amount of ingredients is appropriately increased.
