Coatings repair

Rotating parts should be balanced before coating in order to minimise balance corrections to coated areas. By minimising the area to be recoated, a final check balance after coating repair may not be required. 

Industrial flooring Protective coatings Repair mortars... 

It is more difficult to combat internal corrosion than external corrosion. Internal corrosion can be mitigated by having an internal coating or lining. For internal coating repair, the pipeline will have to be completely out of service. The pipeline need not be out of service for external recoating operations. 

Keywords Coating, anticorrosion, extrusion, powder, adhesion, modified polypropylene, electrostatic spray, fluidized bed, epoxy, insulated coating, repair, field joint... 

Triggered inhibitor release and substrate protection (a) self-healing organic coating repair (b) and inhibitor replenishment of healed coating (c)... 

Ziac foil coated with a conductive, pressure-sensitive adhesive is used for repair of other ziac coatings or for imparting corrosion resistance at field sites. The 0.08-mm ziac tape or sheet has a 0.025-mm coaductive adhesive. The laminate is cut to size and pressed tightly to activate the adhesive. Conductive tape can be wrapped around pipe, especially around welds or connections. The corrosion resistance of this material is iatermediate between galvanized or thermally sprayed coatings and zinc-filled paints (21,50). 

Filtration and water-knockout systems are used to clean up the gas before it enters a compressor. Cooling systems are sometimes required to maintain compressor discharge temperatures below 54°C to avoid damage to the pipeline s protective coatings. Automated compressor stations are typically staffed by maintenance and repair personnel eight hours per day, five days per week. Other stations are staffed on a 24-hour basis because personnel must start, stop, and regulate compressors in response to orders from the dispatch office. 

Aluminide and sUicide cementation coatings such as TaAl on tantalum and MoSi2 on molybdenum oxidize at slow rates and possess some inherent self-repair characteristics. Fine cracks that appear and are common to these coatings can be tolerated because stable, protective oxides form within the cracks and seal them. Thermal cycling, however, accelerates faUure because of thermal expansion mismatch that ultimately dismpts the protective oxide coating. 

Hard facing of various components in the aircraft gas-turbine engine and in industrial apphcations for textile machinery parts, oil and gas machinery parts, paper-shtting knives, etc, is estimated at 1 x 10 in 1995 with an estimated growth rate of 5% annually. The mix is approximately 45% aerospace apphcations, 55% industrial apphcations. Additionally, repair coatings for gas-turbine blades and vanes is estimated at 500 x 10 . These coatings are primarily deposited by plasma spray, arc-wire, HVOF, and detonation gun techniques. 

Precipitating (cathodic) inhibitors are simply chemicals that form insoluble precipitates that can coat and protect the surface precipitated films are not as tenacious as passive films and take longer to repair after a system upset. 

Automotive Refinish Paints. Paint for appHcation to automobiles after they have left the assembly plant is a significant market. Although some of this paint is used for fuU repainting, especiaHy of commercial tmcks, most is used for repairs after accidents, commonly just one door or part of a fender, and so forth. In order to be able to serve this market, it is necessary to supply paints that match the colors of aH cars and tmcks, both domestic and imported, that have been manufactured over the previous ten years or so. Repair paints for the larger volume car colors are manufactured and stocked, but for the smaller volume colors formulas are suppHed by the coatings manufacturer to the paint distributor that permit a reasonable color match for any car by mixing standard bases. 

Manual painting occurs mostiy during touch-up or repair, and is best suited for piping, railings, and other hard to spray places. The conventional tools for manual apphcation are bmshes, rollers, paint pads, and paint mitts. These methods are very slow but are suitable for unskilled appHcators and allow the painter to work the coating deeply into the surface being painted. 

The evaluation of At/ values together with off potentials are aids in deciding whether coating damage should be repaired. In addition, by comparison with previous results, intensive measurements indicate whether new coating defects have arisen. These could be the result of external foreign forces on the pipeline. 

Deviations from the protection criterion determined by the detailed measurements must be rectified either by digging up the pipe and repairing the coating or by resetting the cathodic protection station or constructing an additional station. The detailed measurements should then be repeated and recorded. 

In the tidal zone and the spray zone (known as the splash zone), cathodic protection is generally not very effective. Here thick coatings or sheathing with corrosion-resistance materials (e.g., based on NiCu) are necessary to prevent corrosion attack [4]. The coatings are severely mechanically stressed and must be so formed that repair is possible even under spray conditions. Their stability against cathodic polarization (see Section 17.2), marine growths, UV rays and seawater must be ensured [4,5]. 

The cost and economics of cathodic protection depend on a variety of parameters so that general statements on costs are not really possible. In particular, the protection current requirement and the specific electrical resistance of the electrolyte in the surroundings of the object to be protected and the anodes can vary considerably and thus affect the costs. Usually electrochemical protection is particularly economical if the structure can be ensured a long service life, maintained in continuous operation, and if repair costs are very high. As a rough estimate, the installation costs of cathodic protection of uncoated metal structures are about 1 to 2% of the construction costs of the structure, and are 0.1 to 0.2% for coated surfaces. 

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