Protective and Marine Coatings
Due to high dosage of zinc dust in total inorganic zinc rich primer, pinholes always happen. For solving this problem you can have 2 ways: One is mist-coat application on zinc rich primer. That is, formulation a mist-coating, normally it is clear vanish or pigmented coating with very low viscosity, apply on zinc rich primer first to close pinhole, we call this layer mist coat, afterwards, apply your 2nd primer or top finish, then you can solve this problem.The second way is to formulate mist-free coating on the 2nd layer. Let us suggest your original second coat is epoxy system --BYK-323 0.1-0.3% in epoxy system (if xylene + Butyl alcohol) or BYK-323 0.1% + BYK-065 (or BYK-052) in epoxy system (if xylene only) Alcohol makes BYK-323 more incompatible, get stronger defoamering effect Xylene makes BYK-323 more compatible, more levelling effect but less defoaming effect or even foam stabilizing Xylene 80% + Butyl alcohol 20% makes BYK-323 Levelling effect + wet paint (e.g. epoxy) penetration to pin hole + no foam stabilization In this case, it is not necessary for you to use mist coating and you can avoid pinhole problem (less time, less paint, less painter labor cost).
Of our product range you can try BYK-411. Please follow the instructions in our datasheet. The higher the pigment contents in alkyd, the better the efficiency of BYK-411.
For your inorganic zinc primer system, try with DISPERBYK-103 or DISPERBYK-110, dosage 0.5% in total formulation. For your organic zinc primer system, try BYK-9076 or BYK-P 104 0.5% in total formulation. It has been confirmed by cross-section that by suing those recommendation additives, you can get much more homogeneous zinc dust distribution in your paint film, and, salt spray test demonstrate that with those additives your paint can get better anti-corrosion performance. BYK-410 can be used as rheology for anti-setting and anti-sagging purposes.
Try with DISPERBYK-110, or DISPERBYK-142, or ANTI-TERRA-U 100 with a dosage of 1-2% solid additive calculated on clay. If your system is solvent-free epoxy, then can use DISPERBYK-111, or DISPERBYK-145, or ANTI-TERRA-U 100 which is solvent-free version wetting and dispersion additives specially recommended for epoxy system. By the way, it has been confirmed that soy lecithin used in paint system will reduce anti-corrosion performance.
To get a good orientation and no settling of the aluminium flakes you can use a combination of additives. First of all use a wetting and dispersing additive like DISPERBYK-110 or BYK-P 104 with a dosage of 3% calculated on solid aluminium. And you are right: BYK-410 can help in anti-sedimentation. For the orientation, waxes and silicones are used e.g. CERAFAK 106, CERAFAK 110 or Ceratix types which give orientation and anti-sedimentation. As silicones BYK-333 can be used.
For most types of OH-functional fluorocarbon resins, dissolved in aromatic solvents/ esters, we suggest our DISPERBYK-2025 or DISPERBYK-140 to disperse both inorganic and organic pigments in this binder. The additive dosage is as follows: Titanium dioxide: 2% additive solid on pigment, Inorganic pigment: 10% additive solid on pigment, Organic pigment: 30% additive solid on pigment, Carbon black: 50% additive solid on pigment. DISPERBYK-2025 and DISPERBYK-140 are very good for almost all kinds of organic pigments and carbon black dispersing, in case you want to disperse DPP type organic red pigment, please use DISPERBYK-166 as dispersion agent. It will get good results.
We have a variety of products that are used to improve the application properties of effect pigments containing coatings include non-leafing aluminium. Let us try to give you a brief overwiev: As wetting & dispersing additives we have DISPERBYK-110 and DISPERBYK-162, which are used in quantities of about 1-2% solid additive on solid aluminium. Depending upon the treatment of the aluminium, either DISPERBYK-110 (for basic treated pigments) or DISPERBYK-162 (acidic treatment) are used. A main impact on appearance of effect pigment containing coatings has the wax that is used. We have a variety of products that are used in this area such as Cerafak 103, Cerafak 106 or rheologically modified products (Ceratix 8461 and Ceratix 8463). Finally also certain silicones are used to improve appearance: But here only products should be used, that have no impact on surface tension reduction such as BYK-320 and BYK-322. In order to achieve a perfect result, all three product classes (Wetting & dispersing additive, wax and silicone) are being used in combination.
As you know the stability of the system depends on many parameters (e.g. resin, co-solvents, pigments, manufacturing process...). Due to their high surface tension the leafing pigments are not wetted by the binder and therefore float on the wet film. This effect is achieved by the use of e.g. stearic acid as lubricant. These lubricant could be oxidized and gives then no protection of the aluminium part anymore and therefore you will see the greying at the end. The leafing behaviour depends on the solvents, resin polarity, acid value and at least on the water content in different substances. This is what you´ve to proof in your entire formulation and change to the other direction if necessary. In a paint system with strongly polar co-solvents there is always the possibility that the leafing pigments will drop down (drown) through wetting and turn into non-leafing pigments which gives you then a worster visual appearance. The other possibility is to change the aluminium pigment from 4L to e.g. STAPA LUXAL 4 VS. The STAPA LUXAL 4 VS is nearly the same compared to the 4L, however it has a better stabilized surface area which might help in your system as well. Does adding extenders to alu pigments decreases color stability? Generally not!
General speaking could you use as a rheology additive either our BYK-420 or BYK-425. BYK-420 is a solution of modified urea to give thixotropic flow behavior. Dosage level between 0.3-1.5 on total formulation. This product provides you excellent anti-settling properties even if you're working at lower viscosities. This product needs no pH- or temperature control. Therefore you have easy handling properties with this kind of product. BYK-425 is a solution of a urea modified polyurethane with pseudoplastic flow behavior. It is VOC- and APEO-free and shows a broad compatibility with many aqueous binder systems. Dosage level between 0.1 - 2 on total formulation. The usage of wetting and dispersing additive is also related to the resin. E.g. for amine neutralized resins the recommendation is DISPERBYK-180 or DISPERBYK-184. When a polyurethane is used you have to switch either to DISPERBYK-187, DISPERBYK-190, DISPERBYK-194 N or DISPERBYK-2010.
To avoid sedimentation the first step is to use the right type and the right amount of wetting and dispersing additive. Try with 6-10% of DISPERBYK-103 calculated on SiO2. The additive dosage might be higher to get a stable system. Next step is to do trials with a rheological additive to avoid sedimentation. Try with BYK-410 with a dosage of 0,1-0,3% on total formulation.
Yes, you are right, the problem mainly due to the flocculation of titanium dioxide. To avoid this kind of phenomena, right additive and right additive dosage are both important. Try with DISPERBYK-110, or DISPERBYK-111 and BYK-220 S in the epoxy part during the grinding of the pigment. The dosage is 2% of solid additive of titanium dioxide.
Yes, you are right, organic pigment like phthalo blue, phthalo green and carbon black are those most difficult pigments to be wetted, dispersed and stabilized. You should think about if you are using the right ones and the right amount of wetting and dispersing additive. As a general guide, you can use DISPERBYK-110 for DISPERBYK-180 for TiO2 dispersion (2% solid additive on total TiO2), BYK-9076 or DISPERBYK-2150, DISPERBYK-2025 for organic pigment dispersion, the dosage is: 30 to 50% solid additive to total organic pigments. If it still not good enough, then you can additionally add BYK-SYNERGIST 2100 which is specially for phthalo blue, green and carbon black, only very small amount in total formulation – 3-5% on organic pigments or carbon black. This additive used for high quality top finish paint when need extremely low (colour) delta E and high gloss.
I think the best way to avoid this problem is: to use well dispersed /stabilized pigment concentrate, you should ask the colorant producer for some advice as well or use a different colorant. For the post addition, you can use DISPERBYK-102 or DISPERBYK-2096. But keep in mind, post addition to improve black floatation always need high dosage compared to added at grinding stage.
Glossy film surface (paint) always needs good pigment wetting and dispersion and stabilization together with good defoaming, good levelling. That means, deflocculation wetting and dispersion additive is prefer – better pigment dispersion getting higher gloss, reducing viscosity leads better levelling, and ease air-release/defoaming. Suggest use DISPERBYK-110 with a dosage of 2-5% calculated on filler in your system plus BYK-A 530 or BYK-A 555 0.3-0.8% on total formulation as air release and/or defoamers together with BYK-320 0.1-0.3%. Meanwhile, rheology additive selection also very important, to get glossy surface, it is better use thixopy additive rather than pseduplastic additive. Our additive BYK-410 has very good for anti-setting/anti-sagging together with good levelling property compare to typical polyamide type or castor oil type, fumed silica type, organo clay type rheology additives.
For waterbased epoxy pigmented coatings BYK-DYNWET 800 N should be tested for substrate wetting. For leveling BYK-333 should be tested. Defoaming/pin-hole is always big challenge for waterborne epoxy system. Normally we use defoamer in waterborne system higher dosage than solventborne system. Suggest try BYK-011 or BYK-012, BYK-016 0.5-1.5% in total formulation. To avoid pin-hole, you also can use BYKETOL-WS. It is a levelling additive with defoaming property which can also be used to keep film surface longer opening time after application, it is helpful to avoid pin-hole problem. In Co-grinding of pigments where a lot of extender is used we achieved good results with DISPERBYK-190. It is also possible to use DISPERBYK-181, DISPERBYK-191, DISPERBYK-194 N.
ANTI-TERRA-250 is a controlled flocculating wetting and dispersing additive for water-borne systems. Water-borne coating systems containing inorganic pigments and extenders tend to settle and separate. Due to controlled flocculating the additive forms a network via hydrogen bonds by association between molecules which prevents settling of inorganic pigments. Additionally a combination with BYK-D 420 is recommended in high-filled formulations with extenders of higher density.
BYK-430 provides excellent sag control due to pseudoplastic flow behavior and fast viscosity recovery after application. It is a liquid product and very easy to handle. Optimal results are achieved when incorporated into the mill base during the grinding stage. The typical temperature increase during grinding up to 40°-50°C supports the incorporation.