I believe that almost all construction teams have encountered such a problem: why is the color of this coating different from that of the last one? This is the color difference of the paint. Color difference: due to the difference between the color phase, lightness and color of the coated film and the standard plate or the whole color phase, lightness and color.
The main factors affecting the color difference of coating (1) coating thickness
The thickness of the coating is closely related to the application environment. The factors such as the color of the base material and the gloss change of the coating due to the thickness change must be fully considered in the color matching and even the coating process. (2) The volatilization rate of solvent affects the surface leveling, luster, orientation arrangement of pigments and fillers, and then affects the color phase of the coating. (3) The hydrophilicity of solvent in high humidity environment, if the temperature changes dramatically, in the process of solvent volatilization, the temperature difference on the coating surface occurs due to solvent volatilization, resulting in the enrichment of thin layer water mist on the coating surface, resulting in the whiteness of the coating and color difference. (4) Due to the difference of coating uniformity, the influence degree of color saturation is different due to the adjustment of pigments; due to different construction methods, different operation habits and other factors, the same color is easy to produce color spots on the surface of the same plate, the thickness differences between different plates and other color depths, and the color differences caused by these factors can only be overcome by operating procedures or proficiency.
Cause 01 paint itself causes floating color and infiltrating floating color: floating color is made up of pigments with large density difference, which is easy to produce differences in pigment distribution between the upper and lower layers, making the surface and internal color of the coating film inconsistent. For example, the gray paint mixed with carbon black and titanium white, and the light blue paint mixed with titanium blue and titanium white. When the wet film is dry, the uneven evaporation of the solvent causes the poor surface tension and causes the convection phenomenon, which is the driving force to produce the floating color. Color penetration: color penetration is that the color of the primer is penetrated into the top coat, and the color of the top coat is stained and discolored. 1) There are also organic pigments with poor solvent resistance in the primer, which are dissolved by the topcoat and penetrate into the topcoat. 2) The top coat contains solvent with strong solubility, and the top coat is applied before the primer is fully dry.
02. In terms of construction process, 1) the color difference caused by paint floating or paint precipitation, and the mixing is uneven. 2) Cross contamination caused by unclean spraying tools. 3) The film thickness is thinner or thicker than the standard or the baking conditions are not correct. 03 inspection standard 1) inconsistent standard: different evaluation standard and sample plate; 2) different model of testing instrument or measurement method; 3) color migration of standard plate. 04 material 1) the materials used are different or not matched, and there is a large color difference between batches. 2) Uneven base material and different surface roughness will lead to uneven absorption of the applied coating, resulting in color difference of poly currency. 3) The original paint on the surface of the coated object has lost light and faded, and then the spot caused by local repair and spraying is repaired
preventive measure
1) Strengthen the purchase and inspection of paint, and control the same color of finish paint in one manufacturer. 2) The paint should be properly diluted and not easily diluted. 3) Prevent paint from floating and seeping. 4) Before painting, the tools for measuring the ground, especially the paint pipeline must be cleaned to avoid color mixing. 5) Less touch up paint. If touch up is needed, the whole part or the surface with clear demarcation line shall be touched up. When repairing old equipment, the whole repair shall be used as much as possible. 6) Before coating, the base material shall be treated as qualified, flat and with the same surface roughness. 7) The drying time and temperature shall be strictly controlled within the process time, and the drying specifications shall be consistent. 7) Before use, the paint shall be stirred evenly, especially the composite paint, which can only be used after the color in the barrel is stirred evenly. 8) The film thickness shall meet the requirements of composite process specification. 9) The testing instruments of different parts shall be consistent. 10) The color card shall be updated in time, and the standard version management shall be standardized. 11) Use recommended materials. 12) Ensure that the paint is fully mixed in proportion. 13) adopt the correct spraying method. If it is difficult to match the color, adopt the "soft combination" spraying method. 14) before spraying, a piece of paint will be sprayed with a good paint, and the pigment will be dispersed at the same angle in different light. The difference between the color and the original body color will be compared to ensure that the color matching is accurate. 15) Use the manufacturer's color code to select the correct color recipe. Warm reminder: in short, for the problems of painting refresh, we must find a professional construction team to construct. From the above introduction, we can see that there are so many reasons for color difference. If it is not a professional construction team, it is difficult to avoid it. If the color difference is too large, it will be worth the loss.
Source: coating technology and construction skills
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