Study on thickening of water-based inorganic zinc-rich coatings (5)

2.5 The thickening effect of alkali-soluble thickeners on water-based inorganic zinc-rich coatings
The above 3 thickeners will be appropriately added water to thin, and then in accordance with the method of 1.2 to prepare water-based inorganic zinc-rich coating base ingredients. Experiments showed that L-101 and L-119 thickeners were not compatible with the substitlis, and significant stratation occurred within a few hours of addition. The addition of L-605 to the system did not result in significant stratation. The viscosity change of the substit span under the different L-605 additions was tested, and the change curve was drawn as shown in Figure 7. The increase of base viscosity with the addition of L-605 is very small, which indicates that the thickening effect of L-605 on the system is very poor.alkali-soluble thickener is the use of pH in the pH of 8 to 10 in the water ionized soluble expansion state to achieve the purpose of thickening, pH value of 10 is dissolved in water and lose thickening effect, and therefore not suitable for silicate solution in this alkaline environment. Although the L-605 can be better compatible in the system and storage stability is good, but the thickening effect of the system is very poor, not suitable for use alone as a water-inorganic zinc-rich system thickener.
2.6 Effect of different thickeners on the salt spray resistance of the coating film
Experiments were carried out on polyurethane thickeners, cellulose thickeners and gas-phase silica 3 thickeners with better thickening effects, respectively, to thicken the water-based inorganic zinc-rich coating to a better construction state, and to prepare a coating film with a dry film thickness of about 90 m. The storage stability test is carried out on the substation and the coating film is salt-resistant and foggy, and the results are shown in Table 5.single gas phase silicon dioxide to make the coating to meet the requirements of anti-sinking, the amount is very large. A large amount of gas-phase silica not only causes the coating greatly detactable difficult to construct, but also reduces the film tightness and adhesion to the substrate, thus affecting salt spray resistance. This leads to a relatively poor salt spray resistance of sample coating film using gas phase silica thickeners, and in order to improve the compatibness of polyurethane thickeners with inorganic silicate solutions, more organic emulsions need to be added to the substrate before using polyurethane thickeners, and salt mist resistance is mainly associated with organic-inorganic composite systems. Related to the effect, polyurethane thickener itself has less effect on coating film resistance to salt spray, cellulose thickener in the water-based inorganic zinc-rich coating coating coating on salt spray resistance is the smallest of these groups of tests, this may be cellulose in the coating system with other powders to create synergies and supplement the tolerance of cellulose itself.3 Conclusion
(1) Affected by the very high pH of the base content of water-based inorganic zinc-rich coatings, the thickening effect of inorganic gel thickener is reduced, the alkali-soluble thickener fails, and the concentration bottleneck of inorganic gel thickener pre-gel limits the thickening range of the base material.
(2) Polyurethane thickeners show obvious thickening effect and anti-sinking effect in the organic-inorganic composite substrate system, which can meet the requirements of water-based inorganic zinc-rich coating construction viscosity.
(3) Hydroxyethyl cellulose thickener can be directly added to the base ingredients of water-based inorganic zinc-rich coatings without the need to add organic emulsion, and also shows significant thickening effect and anti-sinking.
(4) HL-200 gas phase silica can improve the viscosity of water-based inorganic zinc-rich substations, but the anti-sinking effect is not good when used alone.
(5) After taking into account the thickening effect, zinc powder subsidion rate, stability of thickened substrate and coating film resistance to salt spray, it is more appropriate to choose SN-612 in polyurethane, HEC-1 and QP-X in cellulose as the substrates of water-based inorganic zinc-rich coatings..