Paint Removal from Metals

In the cross-cut test, which is the most commonly used of the lateral stress methods, knife blades scribe the coating down to the metal in a grid pattern. The spacing of the cuts is usually determined by the coating thickness. Standard guidelines are given in Table 8.2. The amount of paint removed from the areas adjacent to, but not touched by, the blades is taken as a measurement of adhesion. A standard scale for evaluation of the amount of flaking is shown in Table 8.3. 

Acid pickling. In these processes, undesirable oxide coatings are removed from metals - usually ferrous metals - and the surface is prepared for further operations, such as phosphate coating, enamelling, electroplating, painting, etc. The acid of choice has for many years been sulfuric acid. 

Cleanness of the base, i.e. freedom from grease, which improves the wettability of the metal surface, and the removal of oxides, dust or loose paint, etc. already described. The closer the surfaces of paint film and metal, the more secondary valencies originating in the polar constituents of the medium are brought into play. 

Trichloroethylene is also known as Triclene and Vitran and by other trade names in industry. It is a nonflammable, colorless liquid at room temperature with a somewhat sweet odor and a sweet, burning taste. Trichloroethylene is now mainly used as a solvent to remove grease from metal parts. It is also used as a solvent in other ways and is used to make other chemicals. Trichloroethylene can also be found in some household products, including typewriter correction fluid, paint removers, adhesives, and spot removers. Most people can begin to smell trichloroethylene in air when there are around 100 parts of trichloroethylene per million parts of air (ppm). Further information on the physical and chemical properties of trichloroethylene can be found in Chapter 3, and further information on its production and use can be found in Chapter 4. 

For impact tests, ASTM-02794, a ball of known mass was dropped a fixed height through a tube, impacting the coated metal panel. Indirect impact resistance is reported as the fraction of paint removable (pickoff) from the impact site when the panel is struck on the uncoated side. Direct impact resistance is reported as the pickoff at the impact site when the panel is struck on the coated side. Optimally, no coating is loosened by this test. 

A feature of rust, particularly of magnetite (which is an electronic conductor) is its ability to reduce oxygen to a far greater extent than does the metal (Evans and Taylor, 1972). Thus, once some rust has formed, corrosion may be accelerated. This is also one reason why, if all rust is not removed from a metal surface before application of a protective paint coating, corrosion continues under the film. Similarly, akaganeite residues on meteorites promote corrosion under the conditions of ambient humidity and this leads to disintegration of such meteorites in museums (Buchwald and Clarke, 1989). 

All containers, processing equipment, and piping to be used in fluorine Service first must be passivated before use and thereafter designated fui fluorine service. These requirements result from the severe oxidizing characteristics of fluorine gas. Passivation removes any easily oxidized materials, such as paint, pipe dopes, metal oxides, grease, and metal filings. 

Scrap metal generated at stockpile disposal facilities comes from the treatment of metal munitions casings and bulk ton containers (TCs) in the MPF or deactivation furnace system (DFS) after the agent has been drained. Drained bulk containers and munition casings with energetic materials removed and metal munition components are treated in the MPF to destroy any agent residues. After treatment, the metal parts are allowed to cool, vacuumed to remove loose paint flakes and ash residue, and stored temporarily prior to shipment off-site. 

The main problem associated with the application of gun-shot residue analysis is in the interpretation of the results. Lead is a ubiquitous contaminant of the environment, and little reliance can be placed on the presence of lead removed from the hand of a suspect. Barium and antimony are less commonly found in normal control samples however these elements can be present in hand swabs due to metal working, painting and other normal occupations. Also, the suspect must be apprehended soon after the incident and the swabs taken before the hands are washed. Nesbitt et al. [24]... 

Use Removal of greases and oils from metal, plastic, elastomer, and paint or varnish surfaces. Used with all cleaning techniques on assembled motors and parts, electronic devices, precision components, motion-picture film, refrigeration systems, etc. Also used for isolation of viruses, for fire extinguishing, and as dielectric coolants. 

Under certain conditions, dichloromethane (often the major constituent of chemical paint removers) can be converted into phosgene [238,747]. Tobacco smoke, exhaust gases from oil-fired furnaces or petrol engines, and hot metal surfaces are all reported to have a catalytic effect on the reaction [238] ... 

About 6.0 X 10 tons of 30% by mass hydrochloric acid, r C aq), are used to remove metal oxides from metals to prepare them for painting or for the addition of a chrome covering. How many kilograms of pure HCl would be used to make this hydrochloric acid (Assume that 30% has two significant figures. There are 2000 Ib/ton.)... 

Low temperature brittleness to pulverize, e.g., paints off bumpers surfaces or PVC from metal trim at the cryogenic temperatures. The powders are then removed by sieving. 

---