Coatings objectives

Surface Fluorination of Polymers. Fluorocarbon-coated objects have many practical appHcations because the chemically adherent surface provides increased thermal stabiHty, resistance to oxidation and corrosive chemicals and solvents, decreased coefficient of friction and thus decreased wear, and decreased permeabiHty to gas flow. Unusual surface effects can be obtained by fluorinating the polymer surfaces only partially (74). 

The use of nylon-11 for powder coatings or dry coatings (qv) has been developed in response to a growing concern for the environment (44) (see Coating PROCESSES, powder technology). Electrostatic deposition allows thin films to be appHed to metal substrates. Once the powder is appHed, it must be melted and coalesced into a continuous plastic film. Eorced draft or irradiant ovens are used for fusion, and because no polymerization or cross-linkage are required for curing, coated objects can be processed quickly and air-cooled (45). 

In electrochemical protection the necessary range of protection current is achieved by an appropriate arrangement of the electrodes. It follows that measures which raise the polarization resistance are beneficial. Coated objects have a coating resistance (see Section 5.2), which can be utilized in much the same way as the polarization resistance in Eq. (2-45). Therefore, the range in the medium can be extended almost at will by coatings for extended objects, even at low conductivity. However, the range is then limited by current supply to the object to be protected (see Section 24.4). 

Heterogeneous surface areas consist of anodic regions at corrosion cells (see Section 2.2.4.2) and objects to be protected which have damaged coating. Local concentrations of the current density develop in the area of a defect and can be determined by measurements of field strength. These occur at the anode in a corrosion cell in the case of free corrosion or at a holiday in a coated object in the case of impressed current polarization (e.g., cathodic protection). Such methods are of general interest in ascertaining the corrosion behavior of metallic construction units... 

The protection current densities for structures near the sea can amount to 60 to 100 mA m - for uncoated surfaces in the area in contact with water and 20% of that for parts driven into the soil. The land sides of retaining walls take so little current that they do not have to be taken into account in the calculation. With coated objects, the protection current density lies between 5 and 20 mA m . depending on the quality of the coaling. About half this value must be expected for the part in the soil because either the coating is absent or is damaged by the driving. 

There is no precise definition for the frequently used term application fastness of a pigment. It usually refers to the behavior exhibited by a finished product used in accordance with the specifications. The term may thus refer to a print, a coated object, or a plastic product, and the list of features ranges from properties such as lightfastness and weatherfastness to migration fastness and fastness to solvents. In this context, there is a certain amount of emphasis on features which play a role in connection with packaging materials and packed articles. 

Naderveen van H. B., 1980, Hot isostatic pressing of coated objects, in Proc. of 1st Isostatic Pressing Conf, Loughborough University Press, Paper 31. 

Objects of iron are often nickel-plated, or covered with a thin film of nickel, a white, hard metal which preserves its lustre in air, for it is not easily oxidisable. This is done by making the object to be coated with nickel the kathode and a bar of nickel the anode the liquid is a solution of oxalate of nickel and potassium. Iron objects are first coated with copper before nickelling. Silver and gold are best deposited from their double cyanides with potassium these salts are used because the deposit is harder and more uniform than if a halide be used. In thus coating objects, it is of importance that the current density, i.e. the ratio of the current to the area of the surface of the object to be coated, should be considered if this be too high, the metal will be deposited in a loose, flocculent condition. 

One answer to the first question - how to assemble in 3D - is simple use capillary forces. A strategy for self-assembly based on capillarity requires a method of fabricating objects, coating them with thin liquid films (either completely or only on selected areas), and agitating the liquid-coated objects so that they collide to allow coalescence of liquid films (Fig. 4.18). Among the lubricants... 

Owing to remarkable mechanical properties Hke great hardness, scratch resistance and a low frictional coefficient in combination with a high tolerance for aggressive environmental conditions, diamond-coated objects have been developed soon after the first preparation of diamond films. Today the respective products are employed in many technical apphcations. 

The basic mechanism of polymerization is shown in Figure 2.3. A continuous vapor deposition apparatus for coating objects has been described. ... 

The principal use of the carbonyls is that of obtaining pure metals. The Mond process for refining nickel and the preparation of pure iron for special pui oses, such as magnet cores, involve the formation of a volatile carbonyl, transport of the vapors away from impurities in the original metal, and subsequent decomposition to obtain the pure metal. The carbonyls of chromium, molybdenum, and timgsten have been used in mass spectroscopy to determine the stable isotopes of the respective metals. Nickel carbonyl has been used to obtain metallic mirrors and to coat objects with a thin film of metal. Iron carbonyl has been used as an antiknock agent in gasoline. 

If the pigment is omitted, the material is usually called a varnish. The pigmented varnish - the paint - is sometimes called an enamel, lacquer, finish or topcoat, meaning that it is the last coat to be applied and the one seen when the coated object is examined. Lacquers are normally thermoplastic solution paints or varnishes, but the term is sometimes (confusingly) used to describe all clear woodfinishes. Enamels are normally thermosetting paints, hard, with a superficial resemblance to vitreous enamels. 

Encapsulation n. The process of applying a fairly thick coating that conforms to the shape of the coated object. The coating, of either thermoplastic or thermosetting... 

Cobalt chloride (nickel/cobalt alloys and metal-coated objects)... 

Reinforcing steel bars need protection against corrosion. Powdered polymers like EP are applied by fluidised technique. In this process air is used to force powdered polymer into the heated surface of the object, which is in the upper section of a closed tank. The coated object is removed and heated in an oven to assure a continuous coating. 

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