Thick-coat paints

For protective coatings, such as with epoxy paints, the minimum thickness of paint (primer plus paint) should be around 70-80 microns, which is also possible thiough one coat each of primer and paint. If different paint shades are required on outer and inner surfaces paint any one side first, cure it almost completely and then apply the second shade on the other side. Even when there is a wrapping on the second side, can be easily wiped and cleaned, without affecting the first. 

Thin coatings consist of paints and varnishes, which are applied as liquids or powdered resin with a thickness of about 0.5 mm [e.g., epoxy resin (EP) [2]]. Typical thick coatings are bituminous materials [3] and polyolefins [e.g., polyethylene (PE) [4]], thick coating resin combinations [e.g., EP tar and polyurethane (PUR) tar [2]] as well as heat-shrinkable sleeves and tape systems [5]. 

T-wash pretreatment This acid-mordant solution turns the surface black when correctly treated. Problems can occur with use of such an acid solution in situ and from its pungent odor. It must be applied to zinc in a bright condition without corrosion products on its surface. The paint manufacturer s advice must be sought before using under thick coats of two-pack epoxy or urethane. 

Either system can be used manually or as part of an automated plant. Many modifications of the basic spray guns are available, widening the engineer s potential choice of designs. Some equipment allows paint to be sprayed hot, facilitating the application of very thick coats. 

Sprayed aluminium coatings were applied over twenty years ago for a number of buildings in steelworks, notably at Margam, Trostre and Velindre in South Wales. At Margam all steelwork above crane girder level has been aluminium sprayed to 0-10 mm thickness and painted with two coats of... 

Extrusion coating is ideal for rods, tube and wire. The article is passed through a paint reservoir and then out via a die, which leaves only the correct thickness of paint in place. There are further techniques suitable for flat articles in sheet or web form. Knife coating is ideal for very thin coats, especially on continuous paper or plastic webs. The knife is either a metal doctor blade or a curtain of high velocity air (an air knife) directed onto the surface and it removes surplus material applied previously. 

For an adequate barrier against moisture, sufficient thickness of paint must be applied. The modern trend is to apply high-build coatings based on media having high intrinsic water resistance. Such paints may be pigmented with corrosion inhibitors or minerals which impede the flow of moisture through the film. 

Note 5 In calculating paint requirements up to 50% more than the theoretical dry film weight requirement should be allowed to cover thick coatings, wastage, repairs, losses (typically 30% for air spray 15% airless spray 10% electrostatic spray 5% roller or brush) etc. Manufacturers should be asked to quote percentage volume solids in their paint to facilitate calculations. 

When a thick coating (-100-160 ijm) of polyurethane paint Is applied (e.g. specimen 29), the activation energy Is of the order of 26 kcal/mol. This Indicates the higher energy barrier presented by a non-porous coating. 

Paint all connections with a thick coat of nail polish. This will insulate them. Spray paint the outside of the projector body for this reason also. 

The appearance of the surface of the component will be reflected in the appearance after painting—if, say, it is a grained pattern rather than smooth, a grainy effect will be obtained. To some extent this difficulty can be overcome with a thick coat of primer, but obviously it will be helpful from the point of view of quality if the mould surfaces and the natural finish of the material chosen are in keeping (rather than conflict) with the final finish required. 

Adjust and influence coating viscosity (thickness of paint)... 

Figure 4.--Enlarged view of the end grain of painted wood before (top) and after (bottom) swelling with water. The paint is one thick coat of solvent-borne primer. (Upper) Dry. (Lower) Wet (4). (M121 550)...

Figure 5.—Enlarged views of the painted face (top) and end grain (bottom) of a piece of wood similar to that in Figure 4. The crack in the thick coat of solvent-borne primer is over the earlywood-latewood junction and developed after water was placed on the end grain to swell the crushed springwood cells beneath the band of latewood (4). (M121 551)...

Depending on the application, relatively hard distillation bitumen, oxidation bitumen, or high-vacuum bitumen (hard bitumen) are used for physically drying bitumen paints. Waterborne bitumen paints and thick coatings (bitumen emulsions) are produced from moderately hard distillation bitumen. 

Wiping Fast application Uniform fdm thickness High paint yield unsuitable for workpieces with complex shapes exterior coating of pipes application of bitumen to pipelines wood coating... 

Although the dry film thickness on the metal edges is somewhat lower, these areas are still efficiently protected against corrosion. The ultrafiltration technique results in a very high transfer effect and a uniform coating paint solids from the bath are deposited on the metal surface without loss. Since electrodeposition paints have a low organic solvent content, air pollution is low. The dip tank contents are not flammable, which reduces insurance costs [11.5]. 

Thermal sprayed Aluminium/Zinc/Indium - A proprietary variation on thermal sprayed zinc that uses an alloy to enhance the current rather than a humectant. A 300 micrometre thick coating is applied by arc spray. Approrimately 35,000 m had been applied up to May 2003. Adhesive zinc sheet - A proprietary system consisting of rolls of zinc 0.25 mm thick, 25 mm wide with a conductive gel adhesive on one side. The installed system can be painted. The edges must be sealed against water ingress as the gel can swell and leak. 

Uses Film-former, rheology modifier, leveling agent, antisagging agent for low odor solv.-based paints, thick coatings, textured paints, gel varnishes... 

Dip coating (or tumble coating) is ideal for small, mass-produced articles requiring single coat paint application. Quality of finish is not as high as spray coating and control of film thickness is difficult. Solvents used tend to be relatively simple systems of either medium or slow-evaporating solvents, the exact choice... 

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