Maintenance Metal surface

If hardness breakthrough occurs and goes undetected for any length of time, the treatment reserve is swamped and quickly becomes depleted. This loss of treatment is serious because calcium carbonate scaling can result. The reduction in alkalinity also can permit silicate scaling to occur and prevent adequate maintenance of the magnetite film, which protects the waterside metal surfaces from corrosion. 

The records available as a result of leakage surveys and normal maintenance work shall be promptly reviewed for evidence of continuing corrosion. Whenever a buried facility is exposed during normal maintenance or construction activities, a visual examination shall be made of the coating condition and any exposed metal surface. 

Corrosion control of metal surfaces depends on the formation and maintenance of a protective corrosion inhibitor film on the exposed metal surface. This protective film may be established during normal application of a corrosion inhibitor program however, there will be some lag time before the film is completely built up. Metal surfaces that are exposed to the cooling water before the film is completed may become candidates for accelerated corrosion during the initial system operation. Normally, localized corrosion or pitting is common during these early stages of operation. 

Online passivation involves elevating the corrosion inhibitor concentration as high as three times normal maintenance levels. At higher concentrations, the rate at which the protective film forms is accelerated. This, in turn, reduces the degree of initial corrosion on clean but unprotected metal surfaces. The rate at which corrosion protection takes place depends on the temperature, pH and inhibitor used. 

The presence of polyphosphate detergent in the cleaning formulation (some of which will revert to orthophosphate) will, under most circumstances, lead to passivation of the clean metal surfaces. Additionally, as part of the water treatment program start-up procedure, it may prove useful to supplement this initial passivation with 2 to 3x the normal reserve of maintenance inhibitor chemical treatment for a period of 1 to 2 weeks. 

An acid papermaking environment is corrosive. In the same manner that acidity can affect the reasonable life expectancy of paper by breaking down the amorphous structure of cellulose, acidity can affect the reasonable life expectancy of the working parts of a paper machine by corroding the exposed metal surfaces. An alkaline papermaking environment is noncorrosive, extends life, and reduces maintenance costs. Paper machine systems get dirty, and dirt affects the quality of the paper. 

An alternative is to employ anodic protection that relies on the formation and maintenance of protective films on metal surfaces by means of externally applied anodic currents. 

Tompkins (1978) concentrates on the fundamental and experimental aspects of the chemisorption of gases on metals. The book covers techniques for the preparation and maintenance of clean metal surfaces, the basic principles of the adsorption process, thermal accommodation and molecular beam scattering, desorption phenomena, adsorption isotherms, heats of chemisorption, thermodynamics of chemisorption, statistical thermodynamics of adsorption, electronic theory of metals, electronic theory of metal surfaces, perturbation of surface electronic properties by chemisorption, low energy electron diffraction (LEED), infra-red spectroscopy of chemisorbed molecules, field emmission microscopy, field ion microscopy, mobility of species, electron impact auger spectroscopy. X-ray and ultra-violet photoelectron spectroscopy, ion neutralization spectroscopy, electron energy loss spectroscopy, appearance potential spectroscopy, electronic properties of adsorbed layers. 

The deposition of fission products on primary circuit surfaces and, in particular, on the reformer tube walls causes difficulties during maintenance and catalyst refilling procedures, if the activity is intolerably high. Cesium and silver isotopes released during reactor operation are of major concern. Particularly silver diffuses easily out of the fuel elements at operating temperature conditions into the coolant and migrates easily into metal surfaces and is difficult to remove in decontamination operations [32]. 

In most techniques for studying adsorption on metals, xmiform, clean, and reproducible metal surfaces are difficult to prepare and the adsorption process cannot be followed continuously [2, 3,4,7,10,11,16, 18,2l]. Clean and reproducible metal surfaces are also difficult to prepare and maintain in methods that measure adsorption continuously and directly on a metal-coated window of a Geiger tube [l, 6,7,13]. A recently developed apparatus and technique provide controlled conditions for the production and maintenance of relatively clean metal films and the precise measurement of adsorption [20j. Metal is evaporated onto a mica window supported within a high-vacuum apparatus adsorption onto the metal film is measured directly and continuously by a counter tube below the window. 

The most common acid solvent is inhibited muriatic acid. It is inhibited, as all acids solvents must be, to reduce chemical attack on metal surfaces to an acceptable level. Muriatic acid is cheap and effective. It forms reaction products that are generally water-soluble and so are removed in the used solvent. Sulfuric acid is seldom used because of its insoluble reaction products. Nitric acid cannot be prevented from attacking carbon steels or copper alloys. It has certain special applications where the substrate metal is stainless steel or aluminum. Of special interest for small-scale maintenance cleaning by plant personnel is sulfamic acid, mainly because it is a dry solid product that is safely to handle. It has acid properties only after it is dissolved in water. Solid inhibitors and wetting additives can be premixed into the packaged product. 

Chem. Descrip. Polymeric surfactant in methoxy propyl acetate Uses Pigment dispersant, film-former for solv.-based industrial paints, esp. baking enamels and high solids coatings, and automotive, maintenance, construction, machine, and furniture coatings has various binder props, such as adhesion on metal surfaces, corrosion inhibition, and film coherence Features Highly effective... 

Copper and some copper alloys do exhibit corrosion under advanced velocity conditions. Their corrosion resistance is dependent on the growth and maintenance of the protective layers formed on the metal surface. The maximum velocity recommended for copper in seawater is 0.9 m/sec. Alloying with nickel or aluminum increases the resistance of copper alloys to impingement attack [72,79]. 

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