Pollutants cause corrosion

Air pollution causes corrosion and deterioration of ferrous and nonferrous metals, stone, concrete, ceramics and glass, and a host of organic materials paint, paper, photographic emrrlsions, textiles, textile dyes, and leather. It also causes deterioration of crdtural property architectural monuments, mirseirms, hbraries and archives, and stained... 

Vapors emitted from the materials of closed storage and exhibit cases have been a frequent source of pollution problems. Oak wood, which in the past was often used for the constmction of such cases, emits a significant amount of organic acid vapors, including formic and acetic acids, which have caused corrosion of metal objects, as well as shell and mineral specimens in natural history collections. Plywood and particle board, especially those with a urea—formaldehyde adhesive, similarly often emit appreciable amounts of corrosive vapors. Sealing of these materials has proven to be not sufficiently rehable to prevent the problem, and generally thek use for these purposes is not considered acceptable practice. 

At other times the burning of waste products in furnaces to save fuel and reduce pollution has caused corrosion and tube failure. 

Ethene and propene are produced as bulk feedstocks for the chemical (polymer) industry and therefore their purities are important parameters. In particular, H2S and COS are compounds which may not only cause corrosion problems in processing equipment, but also may have detrimental effects on the catalysts in use. Eurthermore, air pollution regulations issued by, among others, the US Environmental Protection Agency (EPA) require that most of the sulfur gases should be removed in order to minimize Sulfur emissions into the atmosphere. Therefore, these compounds have to be determined to the ppb level. 

In certain plants, especially in the chemical industry or in the neighborhood of such plants, the air is often polluted with acidic and corrosive gases that can cause corrosion in the compressor and the compressed air system. Special filtration methods and/or materials may have to be used and the supplier should be consulted. 

The chemical events described above are the basis for the removal of arsines (R3 As) in crude oil or in raw gas condensates, which are known to cause major environmental pollution, equipment corrosion and reduction of catalyst life time (including automotive converters). It was recently demonstrated that these compounds can be completely removed by feedstock hydrotreatment on nickel-based catalysts under FI2 at 160-200 °C [140]. 

Chloride ion is one of the most important natural pollutants influencing corrosion particularly in the tropical humid conditions of Cuba and Campeche in Mexico however, its role may change depending on climate. A very humid climate can cause a fast leaching of the chloride ions and decreases its effect on the acceleration of corrosion rate. A different acceleration rate has been reported for chloride ions between Eastern and Western Caribbean... 

Acid rain causes corrosion of some metals, erosion of marble (limestone), mortar etc. It is responsible for the destruction of softwood forests and for the pollution of ground water. 

Hydrogen sulfide and other sulfur compounds are objectionable in natural gas because they cause corrosion and also form air-polluting compounds during combustion. Carbon dioxide in the gas is objectionable because it lowers the heating value of the gas. 

Sulfur compounds pose a dual problem. Not only do their combustion products contribute to atmospheric pollution, but these products are also so corrosive that they cause severe problems in the operation of gas turbines and industrial power plants. Sulfur pollution and corrosion were recognized as problems long before the nitrogen oxides were known to affect the atmosphere. For a time, the general availability of low-sulfur fuels somewhat diminished the general concern... 

As alluded to in Chapter 8, the ideal biomass feedstock for thermal conversion, whether it be combustion, gasification, or a combination of both, is one that contains low or zero levels of elements such as nitrogen, sulfur, or chlorine, which can form undesirable pollutants and acids that cause corrosion, and no mineral elements that can form inorganic ash and particulates. Ash formation, especially from alkali metals such as potassium and sodium, can lead to fouling of heat exchange surfaces and erosion of turbine blades, in the case of power production systems that use gas turbines, and cause efficiency losses and plant upsets. In addition to undesirable emissions that form acids (SOx), sulfur can... 

Pollutants that will cause corrosive structural damage, in no case discharges with pH lower than 5.0, unless the works is specifically designed to accommodate such discharges... 

An analogy (due to Reynolds) has been postulated relating these three flux terms, which has been verified by numerous classical experiments, usually under conditions which are mathematically tractable. Our interests here are with removal from the air stream of pollutants, which in turn react with the surface and cause corrosion. This process is referred to as dry deposition, although the presence of a liquid (water) film on the surface is essential for rapid removal of soluble gases such as SO2. The presence of such a film could require a two-layer analysis including phase changes, which is beyond the scope of this preliminary inquiry. 

Sulfur compounds in crude oil sharply decreases the quality of fuels and oils produced from the crude oil. They cause corrosion of equipment during treatment, reduce activity of antidetonation additives and antioxidizing stability of gasoline, raise the propensity to form hard residues in cracking gasoline fractions, and result an environment pollution. 

Water, the universal solvent, Is everywhere around us. While additives can actually Improve water quality for some uses, water impurities can cause corrosion and fouling of equipment and be a source of disease and pollution. Automated analysis is the key to solving critical water quality problems. Fast detection and correction of abnormalities are also important steps towards cutting treatment costs and keeping a plant in compliance with regulatory statutes. 

Depending upon the source of the cmde oil, the refining process, and the fuel grade, varying amounts of sulfur may be present in different types of fuel oils. Combustion of the sulfur containing fuel oils produces sulfur oxides, which pollute the atmosphere and cause corrosion problems in boiler equipment. They may form sodium and vanadium complexes, and such deposits on external surfaces of superheater tubes, economizers, and air heaters cause equipment corrosion and loss of thermal efficiency. 

The significance of dust is mentioned above. Industrial and urban atmospheres contain more or less solid particles consisting of carbon, soot, sand, oxides, and salts, e.g. chloride and sulphate. Many of these substances attract moisture from the air some of them also attract polluting and corrosive gases. The salts cause high conductivity, and carbon particles can lead to a large number of small galvanic elements because the particles act as efficient cathodes after deposition on the surface. 

NOj , CI2 and SO c cause corrosion. In addition to the above concerns, emission of pollutants such as HCl, CO2, unbumed hydrocarbons, soot, particulates, dioxins, furans, and volatile organic compounds and metals have received increased attention from many countries around the world. The concerns over pollutants, which are produced as by-products from the direct result of the combustion process [40], are common to aU combustion sources. 

Sulphates in particle form have been shown to cause corrosion in laboratory studies/ but not in field studies. This presumably is because polluted air has decidedly lower concentrations of sulphate than S02 Moreover/ sulphate particles are deposited very much more slowly than SO2. 

Little quantitative work has been carried out to determine the role of non-sulphur pollutants such as nitrogen oxides/ ozone and chlorides in causing corrosion. 

Seawater Titanium resists corrosion by seawater up to temperatures as high as 260°C. Titanium tubing, exposed for 16 years to polluted seawater in a surface condenser, was slightly discolored but showed no evidence of corrosion. T itanium has provided over 30 years of trouble-free seawater service for the chemical, oil-refining, and desalination industries. Exposure of titanium for many years to depths of over a mile below the ocean surface has not produced any measurable corrosion. Pitting and crevice corrosion are totally absent, even if marine deposits form. The presence of sulfides in seawater does not affect the resistance of titanium to corrosion. Exposure of titanium to marine atmospheres or splash or tide zone does not cause corrosion. 

Other factors in the atmosphere that cause corrosion or degradation of the coating are UV light, temperature, oxygen, ozone, pollutants, and wind. Types of failures caused by these factors are ... 

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