Dry film thickness, coatings

Type of paint Method of application Coats Dry film thickness (litn)... 

A representative sampling of coated sheets shall be inspected in accordance with AWWA D103, Section 10.5.3 to verify minimum coating dry film thicknesses. 

AppHcation of an adhesion-promoting paint before metal spraying improves the coating. Color-coded paints, which indicate compatibiHty with specific plastics, can be appHed at 20 times the rate of grit blasting, typically at 0.025-mm dry film thickness. The main test and control method is cross-hatch adhesion. Among the most common plastics coated with such paints are polycarbonate, poly(phenylene ether), polystyrene, ABS, poly(vinyl chloride), polyethylene, polyester, and polyetherimide. 

Tanl . Coatings for Hquid cargo tanks ate selected according to the materials that the tanks (qv) ate to contain. Tank coatings protect the cargo from contamination and must be compatible with the material carried. Epoxy systems ate most frequendy selected because they perform well with both aqueous and organic products. A carefully appHed three-coat epoxy system having a dry-film thickness of 225—300 pm can be expected to last for 12 years. 

Blistering is influenced by the total film thickness as well as by the application conditions and the coating material. A minimum dry film thickness of over 250 is required, and this does not take account of the antifouling component [10]. 

Take wet-film thickness for each coat applied and confirm that they are such as to yield the specified dry-film thickness. 

Measure the dry-film thickness of each coat over a representative area and ensure that the specified film thickness has been attained. 

In the case of a paint coating the film thickness may be determined when the film is dry or when it is still wet both methods are described and discussed in detail in BS 5493, but some discussion is appropriate here. 

The paints were spray applied to a number of substrates. Two coatings gave a final dry film thickness between 85 to 130 microns. For ac impedance studies the coatings were applied to shot (steel) blasted cold rolled steel plates. For interface metal-loss studies by electrical resistance the coatings were applied to 10 micron Fe foils (99.85 purity), adhesively attached by Araldite 2003 epoxy paste on one side to grit blasted glass plates. 

Polymer films of approximately 1000 microns wet film thickness were laid down with a bar applicator on PTFE coated glass panels and the solvent allowed to evaporate at ambient temperature for a standard period of seven days. A typical plot of solvent weight loss with time is shown in Figure 2. The thickness of the wet film was dictated by the need to have adequate mechanical strength in the dry films in order that they might be suitable for subsequent mechanical test procedures. Dry film thicknesses were approximately 300 microns as measured by micrometer. The dried polymer films were examined by dynamic mechanical thermal analysis (DMTA) (Polymer Laboratories Ltd.). Typical DMTA data for a polymer and paint are... 

Coatings from the resins in Tables III and IV The resin (5.0 g, warmed with steam to just liquify it) and a solution of 0.042 g of p-toluenesulfonic acid in 1.0 g of 2-heptanone were mixed until homogeneous, and then HMMM (3.33 g) was added and mixed. In other experiments the resin/HMMM ratio was varied. The mixtures were cast onto 3"x9"x24 ga "Bonderite 1000" steel panels. A //36 wire drawdown bar was used, leading to dry film thicknesses of 18 to 24 im. The... 

AF polymers can be extruded, compression and injection-molded, solution or spray-coated as well as spin-coated from solution. A representative plot showing the dry-film thickness obtained by spin-casting from two different concentration AF solutions at different spin speeds is shown in Figure 2.8. It is possible to prepare multiple coats of AF using this technique. Although most of the solvent is removed in the spin-coating step the polymer must be heated above its glass transition temperature to ensure removal of the last traces of solvent. 

The ZA was added to the resin at 1.5% on resin solids and thereupon dispersed using a Cowles mixer at high speed for 10 min. All coatings were applied by spraying at 0.051 mm dry film thickness and cured at 77°F, 50% relative humidity for 168 h (alkyd) or 375°F for 12 min (polyester). 

Polyester coating. A high solids polyester baking enamel (Cargill 5776) was prepared and spray-applied to yield a 50 jum dry film thickness (Table 4). 

The panel used was cut from selected poplar wood to the dimensions, 6 x 12 x 1/4 inches. Two coats of paint were applied to these panels to provide a dry film thickness of 0.004 inch. 

Test Site. The second phase of this investigation was conducted in the hangar deck structure. The walls and floor of the compartment are of brick, the roof is of steel. The front is designed with ten equidistantly spaced 3-foot-square portholes, arbitrarily numbered from 1 to 10, from left to right, when facing the structure. Tests were conducted on painted 1/8 inch thick steel panels which were fitted over the ports flush with the inner wall, painted surface toward the outside. The initial series of tests was conducted on panels with a dry film thickness of 3 to 5 mils (representative of two top coats) the second series of tests was determined on panels with a dry film thickness of over 5 mils (representative of four top coats). 

Figure 4 shows the insulative ability of the above formulation. Three coats were applied over a primer to a total dry film thickness of 20 mils, allowing 24 hours dry time between coats. This graph indicates complete failure in 8 minutes. When subjected to other tests the coating lacked adhesion to metal, moisture resistance, and flexibility. After, puffing, the coating disintegrated under vibration. 

Coating thickness was measured both wet and dry. Wet thickness measurements were taken using a Gardner s Company Precision Hot Cake, which can measure between 125 and 500 pm films with a 2a uncertainty of +10%. Dry film thickness measurements were taken using an ElektroPhysik s Exacto FN gauge, which can measure between 0.1 and 2000pm with a 2a uncertainty of 3%. 

A primer surfacer, composed most often of a polyester to be cross-linked with a blocked isocyanate or melamine cross-linker, is applied next at a dry film thickness of approximately 1.0 mil by conventional spray application. The function of this coating is to provide filling and leveling properties as well as some stone-chip resistance. Cure conditions range from 250 to 325°F for 20 min. 

The solvent-borne basecoat, consisting of polyester or acrylic binder to be cross-lined with melamine or isocyanate, is applied at a dry film thickness of between 0.6 and 1.5 mils, depending upon the color. Poorer-hiding colors, such as red and white straight shades, require the higher film builds, whereas metal lies and darker colors are applied at the lower film builds. The solvent-borne basecoat is allowed to flash-ofif solvent for approximately 3-5 min at ambient conditions prior to application or the solvent-borne clear-coat. This process is referred to as a wet-on-wet application because the basecoat is not in its cured or cross-linked state. 

The solvent-borne clear-coat is spray-applied over the basecoat at a dry film thickness of 1.8-2.0 mils. The clear-coat, responsible for UV protection, chemical resistance, chip resistance, and so on, is most often composed... 

From a practical point of view, the attainment of the specified dry film thickness is important. In many cases, a minimum thickness must be achieved or protection will fail in a short period. This aspect demands skill in application and close inspection and control. For metallic zinc paints, the thickness would normally be of the order of 60-100/im, for anticorrosive pigmented paints, together with top coats, 100-200 //m, and for inert barrier types 150-300/im. For special environments or projects, these thicknesses may be varied but it should not be presumed that protection will always be improved or be more effective over a longer period of time by increasing the film thickness. 

The most widely used method of application in heavy industrial projects is airless spraying. This utilises high pressure, the liquid paint being ejected through a fine specially designed nozzle which causes the paint stream to break up into fine droplets in the form of a fan. This rapid method of paint deposition also allows application of high dry-film thickness with each coat, 150 /an being not unusual in this respect. A coat of "decorative paint applied by brush would probably yield a thickness of 30-40 fim. 

Thin solid films of polymeric materials used in various microelectronic applications are usually commercially produced the spin coating deposition (SCD) process. This paper reports on a comprehensive theoretical study of the fundamental physical mechanisms of polymer thin film formation onto substrates by the SCD process. A mathematical model was used to predict the film thickness and film thickness uniformity as well as the effects of rheological properties, solvent evaporation, substrate surface topography and planarization phenomena. A theoretical expression is shown to provide a universal dimensionless correlation of dry film thickness data in terms of initial viscosity, angular speed, initial volume dispensed, time and two solvent evaporation parameters. 

High-solids epoxy coatings can be applied at dry film thickness (dft) between 200 xm and 1000 xm in one or two coats. 

The highly protective effects of methacrylate coatings are achieved at a dry film thickness of about 100 [xm. The diffusion resistance to water... 

Dry film thickness (DFT) The thickness of the applied coating on a substrate in completely dry conditions. 

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