Лако-красочные материалы — производство

5.2.6.1 Zinc Hydroxyphosphite In US 4,386,059, a zinc hydroxyphosphite anticorrosive, is described with the theoret­ical formula [2 Zn(OH)2 — ZnHPO3] — x ZnO, wherein x = 0 to 17 [5.88]. This pigment is produced by reacting zinc oxide slurry with phosphorous acid in the presence of a zinc hydroxyphosphite complex promoter [5.88]. It is a […]

Recently, there has been reference in the literature has to further phosphate-based pigments, such as barium phosphate, manganese phosphate, lead phosphate, and chromium phosphate. Utilization of such products has been limited, due to econom­ical aspects [5.71]. 5.2.6

During research for anticorrosive pigments with improved performance properties compared to zinc phosphate, the development of so-called modified polyphosphate pigments was a further focus. Orthophosphates are manufactured using the reaction of orthophosphoric acid with basic and/or amphoteric substances. Polyphosphates are obtained by conden­sation of acidic orthophosphates at higher temperatures [5.54]: • Orthophosphates e. g. 3 […]

As mentioned in Section 5.2.5.1, zinc phosphate, while having many desirable prop­erties as an anticorrosive pigment, does not demonstrate the degree of corrosion protection offered by lead and chromate pigments [5.55]. Therefore the pigment industry has concentrated on developing phosphate-based pigments with improved properties. By controlled chemical modifications under consideration of different points of view […]

5.2.5.1 Zinc Phosphate In order to replace lead and chromate pigments, much attention has been focused upon zinc phosphate. Today, zinc phosphate is one of the most commonly used phosphate-containing anticorrosive pigments. The formulation versatility, due to the extremely lower solubility compared with chromate and other pigments, and therefore the lower reactivity, has led to […]

Barium chromate, and calcium chromate were also utilized in the past as anticorro­sives. Even then, their usage was limited, and therefore does not merit any detailed discussion in this section [5.53]. In general the usage ofchromate anticorrosive pigments has reduced significantly, compared to previous times, due to the fact that they are now classified as […]

This anticorrosive is precipitated from solutions of sodium dichromate, and stron­tium chloride, also followed by filtration, washing, drying and grinding [5.56]. One of the most important uses for strontium chromate has been in primers for appli­cation on aluminum. This pigment still maintains much commercial importance because it is considered to be the most effective anticorrosive […]

This is obtained by reaction of an aqueous slurry of zinc oxide with potassium dichro­mate, and sulfuric acid. It is also washed, filtered, dried and ground [5.56]. Zinc tetrahydroxychromate has been mainly used for the formulation and production of wash and shop primers based on polyvinylbutyrale resins.

This pigment, also called zinc yellow, is produced by reacting an aqueous slurry of zinc oxide or hydroxide with dissolved chromate ions, followed by neutralization, or by precipitation of dissolved zinc salts with dissolved chromate salts, followed by washing, filtration, drying, and milling processes [5.56]. Previously zinc yellow used to hold a major share of […]

Chromates have long been utilized as anticorrosives. The anticorrosive action of chromates is based on the content of a certain amount of water-soluble chromate within these pigments (Table 5.3). Tab. 5.3: The solubility of chromates in water at 25 °C [5.51]. Pigment Formula Grams of CrO3/ 1000 ml of H2O Calcium chromate CaCrO4 17 Zinc […]