Deposit removal

Figure 4.106 As in Fig. 4.10A, with deposits removed to show pitting. 

X-ray analysis of corrosion products and deposits removed from internal surfaces showed 68% iron, 12% phosphorus, 8% silicon, 3% sulfur, and 2% each of zinc, sodium, chromium, and calcium other materials made up the remainder of deposits and corrosion products. 

Removal of deposits and corrosion products from internal surfaces revealed irregular metal loss. Additionally, surfaces in wasted areas showed patches of elemental copper (later confirmed by energy-dispersive spectroscopy) (Fig. 13.12). These denickelified areas were confined to regions showing metal loss. Microscopic analysis confirmed that dealloying, not just redeposition of copper onto the cupronickel from the acid bath used during deposit removal, had occurred. 

Inspect the reservoir interior for rust and other deposits. Remove any rust with scrapers and wire brushes, wash down the interior with a detergent solution, and flush with clean water. Dry the interior by blowing the surfaces with dry air and use a vacuum cleaner to remove trapped liquids. 

Pipe scale, hydrocarbon solids, hydrates, and other deposits removed from piping and equipment prior to transportation... 

Cleaning procedures include an internal washdown with a 0.5 to 2% soda ash solution, using a high-pressure jet. All wash water must be drained and deposits removed from the boiler. Usually, all external surfaces of the boiler are cleaned as well, in addition to the flue gas side of the economizer, air heater, and ID fans. 

Cleaning solution formulations may include one or more deposit removers, plus an appropriate corrosion inhibitor (to protect exposed metal). An antifoam and often a wetting agent [e.g., an alkylarylpoly-ethoxy alcohol with a 12-15 hydrophilic-lipophilic balance (HLB) to improve detergency and solubilization] may also be added. 

Measurements of radionuclides and metals in marine sediments and particulate matter are conducted for a variety of purposes, including the determination of sedimentation rates, trace metal and radionuclide fluxes through the water column, enrichment of metals in specific phases of the sediments, and examination of new sedimentary phases produced after sediment deposition. Such studies address fundamental questions concerning the chronology of deep-sea and near-shore sedimentary deposits, removal mechanisms and cycling of metals in the ocean, and diagenesis within deep-sea sediments. 

On-Line Deposit Removal from Heat Exchangers... 

The persistence of elemental phosphorus in the air is very short due to oxidation to phosphorus oxides and ultimately to phosphorus acids. However, the particulate phosphorus aerosol may be coated with a protective oxide layer that may prevent further oxidation and extend the lifetime of particulate phosphorus in air. Both wet and dry deposition remove unreacted elemental phosphorus and the degradation products from the air. Similarly, elemental phosphorus oxidizes and hydrolyzes in water and in soil. A small amount of elemental phosphorus is lost from soil and water by volatilization. 

Wet deposition removal of atmospheric particles to the Earth s surface by rain or snow. Wetlands habitats that are regularly saturated by surface water or groundwater and subsequently characterized by distinct vegetation. 

Marl (CaC03) deposits, removal of siliceous matter... 

Techniques of tritium removal from co-deposited layers in next-generation tokamaks, such as ITER, have an important impact on machine operation. Attempts are being made to develop in-situ co-deposit removal techniques that would not overly constrain machine operation, both in terms of T removal and plasma performance recovery after cleanup. In addition to machine operation considerations, the tritium in the co-deposited layers will also have safety implications. During a severe accident, the vacuum vessel of an operating tokamak can be breached. If a significant inventory of tritium in the form of a saturated layer is present, much of this tritium can be released as tritium oxide as the film reacts with oxygen. 

Table 10.2. Laser-heating, thermo-oxidation, and plasma discharge techniques for co-deposit removal [ These techniques require the introduction of oxygen into the torus and thus will require conditioning to remove the residual oxygen and water to recover plasma operation. Further work is needed to determine the effects of collateral damage]...

Laboratory Studies of Co-deposit Removal via Thermo-Oxidation... 

To halt deposition, remove the battery from the cell and disconnect the wires from the electrodes. Remove the Cu plate from the solution and rinse the membrane surface with deionized water. The nickel-plating solution can be returned to its original container and reused indefinitely. We have used the same 500 mL of plating solution for approximately 50 depositions without any noticeable change in quality. 

Experiment 171. — a) Dissolve about 10 gm. of aluminium sulphate in the least possible amount of hot water. Dissolve 3 gm. of potassium sulphate in the same way. Mix the clear, hot, saturated solutions in a small shallow dish, and allow the solution to cool undisturbed. Crystals of potassium alum will be deposited. Remove the best ones dry. and examine. Describe them, giving color, luster, size, and crystal form. 

The other removal process, wet deposition, removes sulfur from the atmosphere as sulfates in rain. This would be the fate of sulfuric acid produced via the homogeneous oxidation of SO2, but oxidation also proceeds within droplets. Aqueous sulfur dioxide is oxidized only slowly by dissolved oxygen, but the production of sulfuric acid, which is much stronger, leads to acidification... 

Fig. 4. An aluminum deposit removed from a titanium cathode [130, 132].

In the event this procedure is not effective, the surgeon may need to operate on the blood vessels instead of the brain itself. A graft to bypass the blocked area may be called for or the vessel may be opened and the deposit removed (a procedure called endarterectomy) if the artery is accessible. In addition, an artery can balloon from the pressure of the blood within it. This is called an aneurism, and it forms at the site of a weak spot in the arterial wall. The swollen artery in itself may do no harm, but the weakened arterial wall can burst at any time, allowing the escape of blood into the brain. This is one form of stroke. If the artery is accessible, the sur-... 

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