First, as you know, iron oxide black pigments have a magnetic structure. Wetting and dispersing agents can aid in grinding, but compared to the steric stabilization provided by dispersing agents, stabilizing the magnetic structure of iron oxide black requires much greater force. There are other organic black pigments on the market that are similar in color to iron oxide black but are easier to stabilize. In addition to organic black pigments, low-pigment carbon black is also an option. For high-efficiency wetting and dispersing agents used in co-grinding formulations, Tech-6013 is suitable for both solvent-based and water-based systems, while Tech-6208 and Tech-60701 are suitable for water-based systems.

Defoamers may contain hydrophobic particles and/or bubble-breaking polymers, so they must be stirred thoroughly before use. Another possible cause is variations in shear force during the production process; the more vigorous the mixing, the greater the shear force required and the longer the mixing time. We recommend increasing both the shear intensity and the mixing time.

Rheological behavior has a significant impact on leveling. If a coating exhibits strong pseudoplasticity and high low-shear viscosity, its leveling performance will certainly be poor. Leveling involves striking a balance between substrate wetting and viscosity. In our testing system, we can verify that Tech-9048 and Tech-9040N achieve this balance.

Certain additives, such as defoamers, require high shear forces to disperse once added to coatings. The equipment used for production, such as dispersion tanks, differs significantly from laboratory equipment, resulting in different energy inputs. In such cases, increasing the shear rate or extending the mixing time for the additives can resolve the issue of pinholes.

In addition to the deflocculation and stabilization of carbon black, using the correct grade of carbon black is also crucial. To achieve high blackness or deep blue-phase black, carbon black with an initial particle size of 0.015 µm or less is typically selected. Pigments with such small particle sizes have a very large specific surface area; stabilizing this type of pigment requires selecting suitable wetting and dispersing agents and the correct dosage, since stabilization means that the wetting and dispersing agents completely coat the pigment surface. In all cases, the wetting and dispersing agent must be compatible with the resin system. For solvent-based systems, we recommend Tech-5861, Tech-5561, Tech-6013, or Tech-5076. For water-based systems, we primarily recommend Tech-690.

There are many reasons for the occurrence of color floating and mottling. One reason is incompatibility between the color paste and the resin; another is that the pigments or fillers are not sufficiently deflocculated and stabilized within the system. A third reason is that the pigments are not sufficiently stable within the color paste. If you purchase color pastes from an external supplier, we recommend testing the iron oxide red paste in clear coat and conducting a finger-grinding test. If the iron oxide red is unstable, it will exhibit its own tendency to float and cause mottling. You can try adding products such as Tech-504S or Tech-5011 afterward.

Pitting is a surface tension issue; it may be caused by particles with lower surface tension becoming mixed into the coating, resulting in pitting after drying. In water-based systems, defoamers are typically added; if the defoamer is too strong or incompatible, it can lead to pitting. In any case, the surface tension of the coating must be reduced; you may test Tech-2409 or Tech-28412. If the pinholes are caused by the defoamer, the issue can be resolved by improving compatibility; we recommend increasing shear force and mixing time.