Zinc coatings applications

Separate the metal from the environment with a physical barrier. Many corrosion inhibitors make use of this principal to protect metals. Proper use of an appropriate inhibitor may reduce or eliminate pitting. Pits are frequently initiation sites for corrosion-fatigue cracks. The effectiveness of inhibitors depends upon their application to clean metal surfaces. An example of this method is the use of zinc coatings on steel to stifle pit formation. 

Galvanized steel A zinc-coated steel sheet or plate with good corrosion resistance properties used for ductwork and other applications. 

Sweep blast or abrading This is a suitable method before application of thick two-pack materials but care is required not to remove too much zinc coating. 

Cadmium also provides a sacrificial coating to steel which gives better protection than zinc in applications where strong acids and alkalis may be encountered and those involving immersion in stagnant or soft neutral waters. It should be used in applications involving bimetallic contact with aluminium and in electrical applications where ease of solderability is important. Cadmium has a low torque resistance and should be used as a coating material in cases where bolted assemblies have to be frequently... 

The outstanding virtue of zinc-rich paints is simplicity in application. No special equipment is required and the operation can, of course, be carried out on site, large or small structures being equally suitable for treatment. While there is some evidence that the zinc-rich paints will reduce iron oxides remaining on the steel surface, proper surface preparation is as important here as with traditional paints if the best results are to be achieved. The main use of zinc-rich paints is to protect structural steel-work, ships hulls, and vulnerable parts of car bodies, and to repair damage to other zinc coatings. 

As the protective value of the zinc coating depends largely on the corrosion resistance of zinc, the life of a coating is governed almost entirely by its thickness and by the severity of the corrosive conditions to which it is exposed. Extensive tests and field trials which have been carried out have shown that the life of a zinc coating is roughly proportional to its thickness in any particular environment and is independent of the method of application. 

Zinc poisoning may occur after consumption of products stored in zinc-coated containers. For instance, a dish of curried poultry, which was a source of zinc poisoning, was found to contain 1.0 pg per g. Poisoning may be also caused if the carency period after application of zinc pesticides is not observed. 

Tin—zinc coatings (75 wt % tin) have application as a solderable coating for radio, television, and electronic components. They also provide galvanic protection for steel in contact with aluminum. 

Typical applications of zinc-coated steel and products are given in Table 4.84. 

Often the OEM coatings depend on the nature and condition of the substrate to which paint is applied application methods and conditions drying time required and decorative and protective requirements. The substrate most commonly coated with industrial coatings are iron and steel, but also include other metals such as aluminum and its alloys, zinc-coated steel, brass, bronze, copper, and lead. Nonmetalhc substrates include timber and timber products, concrete, cement, glass, ceramics, fabric, paper, leather, and a wide range of different plastic materials. Consequently, industrial coatings are usually formulated for use on either a specific substrate or a group of substrates. 

The plated composite was sectioned and examined for elemental composition. This analysis showed that the zinc coating on the fiber surface was uniform throughout the length and over the cross-section of the composite. The plating process was simple to operate and control, which suggests that the zinc layer could be regenerated in situ on a spent composite by the application of current while flowing zinc chloride solution. 

Polysilicate. [DuPont] Polysilicate binder for refractory, ceramic, metal, inorg. fiber, catalyst support, inorg. paint systems, zinc coatings findustrial applic. glass surface modifier. 

Galvanized-steel bars can be welded, but loss of the zinc coating may take place in the welded zone the application of a zinc-rich paint should be recommended after cleaning of the welded area. 

The process has been continuously improved [71] but so far a breakthrough in the application of electroplated aluminum is still pending. The problem is the price, compared to zinc coatings. Electroplated aluminum is more expensive than zinc by a factor of 3 to 5. Therefore, electroplated aluminum is restricted to some high-tech applications, for example, special optical surfaces. As a corrosion-protective coating, the material is not yet an alternative to the established systems. 

Other anode systems specially developed are sprayable conductive polymer coatings, metallized zinc coatings, and conductive paints. Typical primary anode for the conductive polymer or paints is platinized niobium wire attached to the concrete prior to application. Estimated cost is 76/m with a service life of five years. 

Figure 16.10 OCP curves of coated PPy zinc electrodes cured In air for 1 h at 180 °C and immersed in 3.5% NaCI solution. PPy films (Ri2iim thick) were synthesized in 2 M NaSac+ 0.5 M Py at pH 5 and 1.9 M NaSac + 0.1 M DISacH + 0.5 M Py at pH 5.4. (Reprinted with permission from Chemistry of Materials, Ultrafast electrosynthesis of high hydrophobic polypyrrole coatings on a Zinc electrode Applications to the protection against Corrosion by E. Hermelin,]. Petitjean, P.C. Lacaze et al., 20, 13, 4447—4456. Copyright (2008) Elsevier Ltd)...

E. Hermelin, J. Petitjean, J.-C. Lacroix, K.I. Chane-Ching, J. Tanguy, and P.C. Lacaze, Ultrafast electrosynthesis of high hydrophobic polypyrrole coatings on a Zinc electrode Applications to the protection against Corrosion, Chem. Mater., 20, 4447 1456 (2008). 

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