Sprayed zinc dust

Flour Mill Dust Sprayed Zinc Dust y sed I... 

T I Flour mil dust Alkali fumes Sprayed zinc dust ------------------... 

Because of its resistance to corrosion, zinc may be used to coat iron. This may be done by dipping the iron into molten zinc or by spraying zinc on the iron articles, for example iron sheets. This is known as galvanising. Smaller iron articles may be coated by heating with zinc dust, a process known as sherardising, or suspensions of zinc may be used in paints. 

Characteristics of coating Hot-dip galvanising A/etai spraying Plating Sherardising Zinc dust painting... 

Technical Notes on Zinc. Separate leaflets entitled Zinc Coalings, Galvanising, Zinc Spraying, Sherardising, Zinc Plating and Zinc Dust are available from Zinc E>evelopment Association, London... 

Averell and Norris (3) have developed an analytical method adapted to the determination of parathion in spray or dust residues, which is sensitive to about 20 micrograms. It is based upon the reduction of parathion with zinc to the amino compound, diazotiza-tion, and coupling with Bratton and Marshall s amine, which gives an intense magenta color with an absorption peak at 555 millimicrons. Bowen and Edwards (6) have used the polarograph to assay technical grades of parathion and its formulations. 

The pure compound is a pale yellow, nearly odourless oil, soluble in organic solvents, but almost insoluble in water. Averell and Norris2 describe the detection of minute quantities of parathion (20 /ig.) in spray and dust, by reduction with zinc, diazotization and coupling with an amine to give an intense magenta colour. It is effective (at concentrations of 25-600 p.p.m.) against many insect species, but of course, like the majority of organo-phosphorus insecticides, it is toxic to man and to animals. 

Iodide (potassium) starch A 1% potassium iodide solution in 80% aqueous acetic acid is sprayed on the plate followed by a 1% aqueous starch solution. A pinch of zinc dust is recommended as an addition to the potassium iodide solution. 

Zinc is frequently applied to the surface of iron or steel by other methods. In the Schoop process, molten zinc is sprayed onto the surface by a blast of air in a manner similar to that used in spraying paint. In addition to metals, objects made of wood, leather, paper, and the like may be coated with zinc by this process. In the process of sherardizing, iron is covered with a thin layer of zinc dust at temperatures of 700 to 800°C. Under these conditions, zinc penetrates the surface of the iron to a considerable extent. 

Figure 8. Zinc dust paints based on an epoxy ester after a 168-h salt spray test in accordance with DIN 50 021 and ASTM B 117-64 left, control paint right, paint containing 2% Aerosil R 972 related to zinc dust mass.

Ethyl silicate zinc dust paints are applied by air or airless spraying, often directly after jet cleaning of the substrate. They are seldom applied with a brush or roller. Layer thicknesses range from 15 to 20 pm (shop primers) through 50 to 70 pm (primers) to >100 pm (single thick-layer application). 

Painting with zinc dust paints entails the same design considerations applicable to all painting projects (BS 4479 Part 4). With zinc-rich paints, adhesion is best achieved by blasting to at least Sa 2 A, and limitations on thin steel apply as with the metal spraying. 

Organic peroxides Hydriodic acid. Spray plate with a reagent comprising 40 ml glacial acetic acid and 0.2 g zinc dust added to 10 ml of 4% aqueous potassium iodide, then spray with fresh 1% starch solution. Peroxides (and certain other types of oxidising agents) revealed by liberation of free iodine. Alternatively use 2,6-dibromobenzoquinone chlorimine. [28]... 

The zinc dust is filtered off and the layer sprayed with I. After an interval of 5 min, II is sprayed on freely until the layer appears transparent. Peroxides are recognised through the blue colour from liberated iodine. 

Uses Zineb is a light-colored powder or crystal. It is a polymer of ethylene (bis) thiocarbamate units linked with zinc. Zineb is used to prevent crop damage in the field and to protect harvested crops from deterioration during storage or transport. It was used to protect fruit and vegetable crops from a wide range of foliar and other diseases. It was available in the United States as wettable powder and dust formulations. Zineb can be formed by combining nabam and zinc sulfate in a spray tank.7121319... 

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