Coatings surface treatments

Key words conversion coating. E-coating, surface treatment. Mg alloys, corrosion. 

Liquid coating technologies used on interior and exterior plastic surfaces are somewhat similar. The range of nonliquid coating surface treatments and performance requirements for interior and exterior automotive surfaces is considerably different as shown in Table 3. 

An important newer use of fluorine is in the preparation of a polymer surface for adhesives (qv) or coatings (qv). In this apphcation the surfaces of a variety of polymers, eg, EPDM mbber, polyethylene—vinyl acetate foams, and mbber tine scrap, that are difficult or impossible to prepare by other methods are easily and quickly treated. Fluorine surface preparation, unlike wet-chemical surface treatment, does not generate large amounts of hazardous wastes and has been demonstrated to be much more effective than plasma or corona surface treatments. Figure 5 details the commercially available equipment for surface treating plastic components. Equipment to continuously treat fabrics, films, sheet foams, and other web materials is also available. 

Corrosion. Ammonium bifluoride dissolves in aqueous solutions to yield the acidic bifluoride ion the pH of a 5% solution is 3.5. In most cases, NH4HF2 solutions react readily with surface oxide coatings on metals thus NH4HF2 is used in pickling solutions (see Metal surface treatments). Many plastics, such as polyethylene, polypropylene, unplasticized PVC, and carbon brick, are resistant to attack by ammonium bifluoride. 

Plastic packagiag materials are thermoplastic, ie, reversibly fluid at high temperatures and soHd at ambient temperatures. These materials may be modified by copolymerization, additives ia the blead, aHoyiag, and surface treatment and coating. Properties of principal plastic packagiag materials are givea ia Table 1. 

Apphcations of microhardness testing greatly extend the conventional indentation hardness test to glass and ceramics, metaHographic constituents, and to thin coatings or other surface treatments not otherwise testable. 

When the operating temperature exceeds ca 93°C, the catalytic effects of metals become an important factor in promoting oil oxidation. Inhibitors that reduce this catalytic effect usually react with the surfaces of the metals to form protective coatings (see Metal surface treatments). Typical metal deactivators are the zinc dithiophosphates which also decompose hydroperoxides at temperatures above 93°C. Other metal deactivators include triazole and thiodiazole derivatives. Some copper salts intentionally put into lubricants counteract or reduce the catalytic effect of metals. 

B. Bhushan and B. K. Gupta, Handbook of Tribology Materials, Coatings, and Surface Treatments, McGraw-HiU Book Co. Inc., New York, 1991 P. J. Blau, Friction, Eubrication, and Wear Technology, Vol. 18 Mmerican Society of Metals (A.SM) Handbook Series, ASM International, Metals Park, Ohio, 1992. 

Lubricant carriers are applied by dippiag the workpiece ia hot solution or slurries such as lime or phosphate coatings. Details of surface treatments are available (5) (see also Metal surface TiiEATiffiNTs). 

Various types of surface coating materials can be used with sohd fiber paperboard to achieve desired package properties. The coatings and treatments described for cormgated paperboard apply to sohd fiber paperboard as weU. Various solvent and aqueous-based polymeric emulsion coatings are also commonly used (see Emulsions). 

Metal Treatment. After rolling, the oxide scale on sheet steel is removed by acid treatment (pickling) (see Metal surface treatments). Phosphoric acid, a good pickling agent, leaves the steel coated with a thin film of iron phosphates. This process improves mst resistance but presents a problem if the steel is to be electroplated. 

The next advance in total hip arthroplasty came with the development of various porous surface treatments which allow bone tissue to grow into the metal porous coating on the femoral stem of the hip implant and on the acetabular component of the total joint replacement. These developments arose because of patients who were not able to tolerate cemented implants because of allergies to the cement, methylmethacrylate. More youthflil patients are better served by a press-fit implant as well. Figure 12 shows the difference between textured and beaded surface-treated orthopedic prostheses. 

Plasma processing technologies ate used for surface treatments and coatings for plastics, elastomers, glasses, metals, ceramics, etc. Such treatments provide better wear characteristics, thermal stability, color, controlled electrical properties, lubricity, abrasion resistance, barrier properties, adhesion promotion, wettability, blood compatibility, and controlled light transmissivity. 

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