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This is PTING proofing three samples, the customers for our appearance to give unanimous praise, of course, from our point of view, the appearance is secondary.
This is a section of a sample from another painted anti-corrosion supplier, and we can see that there is already peeling in the red circle, indicating that the adhesion is not up to standard.
Local zoom comparison can be found, the other side of the sample (the other side of the sample for the top section, the bottom section for the PTING sample) coating in the chamfer edge position is not covered in place. After touching, we can feel that the surface of the coating made by PTING is smooth, while the surface of the sample made by the other party is relatively rough.
We do not agree with the customer's lack of knowledge of the coating technology and judge the quality of the coating only from the aesthetics of the surface of the samples from both sides. PTING repeatedly stressed that we do not look at the appearance, but look at the inner, so at our request, the customer did a destructive test of the coating.
Firstly, we took a razor blade to destroy the coating of another sample and the result was as shown in the picture above, the coating came off in one piece. Then do the same to the PTING sample, the result is shown in the figure below.
Upon comparison we can see that the zinc layer of the other one has been peeled off extensively, the top coat of the sample made by PTING is destroyed, the middle coat is still intact and the zinc layer part underneath is not visible at all.
From the destructive test mentioned above, we can find that the material chosen by the other party is the same as ours, which can be said to be completely fine. But why is the adhesion gap so big? The reason lies in the surface treatment of this detail, did not do. From the zinc layer off parts, it is not difficult to find that the other side of the substrate processing is to choose shot blasting. Shot blasting relative to sandblasting, the efficiency will be much higher, and the cost will also be greatly reduced, but the effect of shot blasting is not in line with the thermal spray zinc processing. After sandblasting, the surface of the workpiece under high magnification will show sharper peaks and valleys, while the peaks and valleys of the shot blasting is more rounded and smooth, imagine how the rounded and smooth surface grips the metal coating. Moreover, the surface roughness (RZ) of the workpiece required for thermal zinc spraying is larger, which is also unattainable by shot blasting. So at the beginning of the choice of pre-treatment process, in fact, has decided the quality of the coating.
Secondly, why is the other side's paint coating rougher than PTING? The reason is that the zinc layer itself is rough, and there are very, very many extremely small pinholes on the surface. Because the pinholes are filled with air, the paint will blister if it is sprayed directly. Therefore, a very thin layer of paint must be applied to remove the air from the pinholes before the subsequent paint coatings can be applied.
Firstly, we took a razor blade to destroy the coating of another sample and the result was as shown in the picture above, the coating came off in one piece. Then do the same to the PTING sample, the result is shown in the figure below.
Upon comparison we can see that the zinc layer of the other one has been peeled off extensively, the top coat of the sample made by PTING is destroyed, the middle coat is still intact and the zinc layer part underneath is not visible at all.
From the destructive test mentioned above, we can find that the material chosen by the other party is the same as ours, which can be said to be completely fine. But why is the adhesion gap so big? The reason lies in the surface treatment of this detail, did not do. From the zinc layer off parts, it is not difficult to find that the other side of the substrate processing is to choose shot blasting. Shot blasting relative to sandblasting, the efficiency will be much higher, and the cost will also be greatly reduced, but the effect of shot blasting is not in line with the thermal spray zinc processing. After sandblasting, the surface of the workpiece under high magnification will show sharper peaks and valleys, while the peaks and valleys of the shot blasting is more rounded and smooth, imagine how the rounded and smooth surface grips the metal coating. Moreover, the surface roughness (RZ) of the workpiece required for thermal zinc spraying is larger, which is also unattainable by shot blasting. So at the beginning of the choice of pre-treatment process, in fact, has decided the quality of the coating.
Secondly, why is the other side's paint coating rougher than PTING? The reason is that the zinc layer itself is rough, and there are very, very many extremely small pinholes on the surface. Because the pinholes are filled with air, the paint will blister if it is sprayed directly. Therefore, a very thin layer of paint must be applied to remove the air from the pinholes before the subsequent paint coatings can be applied.
Thermal sprayed zinc coating surface
In addition to the pre-treatment process, the zinc layer of pre-coating before spraying paint, as well as the angle of sandblasting, sandblasting roughness, zinc film thickness, paint film thickness, air temperature and humidity and so on these details are required to control. Therefore, in the process of coating anti-corrosion, the details determine the success or failure of the coating!
