Corrosion acid deposition effect

Some of the most dramatic environmental effects of acid deposition have involved buildings, statues, monuments, and other structures made of metal and stone. The explanation of this kind of damage is obvious Acids in acid deposition react with metals and with many of the compounds of which rock and other building material are made. For example, corrosion occurs when metals such as iron are exposed to hydrogen ions in the presence of oxygen ... 

Recently, interest in acid deposition has broadened to include special acidic events such as dew, frost, and fog. Little is known about the frequency with which acidic dew occurs, its composition, or its effect on dry deposition rates. However researchers have long recognized that surface wetness contributes to the corrosion of metal surfaces (J ) and to the deterioration of stonework (2). 

NO in combination with SOp has a synergistic corrosion effect especially indoors on electrical contact materials, copper and steel. The influence of acid precipitation may differ for different metals and depends also on the pollution level. The atmospheric corrosion of metals due to acid deposition is in most regions mainly a local problem restricted to areas close to the pollution source. 

In 1981, a field study was initiated by the Bureau of Mines to determine the effects of the environment, including acid deposition, on the corrosion of a number of commonly used metallic materials of construction. This study, which is fully described in a recent paper (6), is being conducted at field sites where continuous air... 

Effects of Acid Deposition on Poultice-Induced Automotive Corrosion... 

A correlation between the corrosivity and the poultice chemistry was made by mounting corrosion test coupons on vehicles in each city and by simulating poultice effects in the laboratory. Results show that corrosion damage increases in a complex manner in areas of heavy road salt use and acid deposition. 

The study revealed very little qualitative or quantitative information on the effects of acid deposition on PCC structures. The rate of deterioration of reinforced PCC structures in polluted areas, however, appears to be increasing, and available information makes it readily apparent that acids and acid waters significantly affect the durability of concrete, and that S02> NOx> and HCl accelerate the corrosion of reinforcing steel. 

Because the literature on the effects of acid deposition on PCC is limited, the large amount of literature dealing with the corrosive effects of acids, acid waters, and sulfates on concrete was reviewed in an attempt to estimate the effects of acid deposition on PCC (25-48). 

Flinn, D. R. Cramer, S. D. Carter, J. P. Spence, J. W. "Field Exposure Study for Determining the Effects of Acid Deposition on the Corrosion and Deterioration of Materials Description of Program and Preliminary Results." Durability of Building Materials pp. 147-175, 1985. 

Corrosion of bronze, commonly termed bronze plague, in the Torrey monument in Mount Auburn Cemetery, Cambridge, MA, due to the effects of acid deposition. (Photo by Robert Baboian.)... 

LCID RAIN IS AN IMPORTANT AND GROWING TOPIC. This book addresses the important materials problems resulting from acid deposition. It is divided into five sections Measurement and Monitoring of Atmospheric Deposition, Metallic Corrosion, Masonry Deterioration, Degradation of Organics, and Economic Effects. 

The section on metallic corrosion clearly indicates that the conventional method of classification of environments into marine, industrial, and rural no longer is adequate. More specific information is needed about the actual chemical components in the atmosphere as well as humidity and other factors. Specific environments also are addressed in the metallic corrosion section. For example, the automotive environment in the northeastern United States is particularly severe because of the combination of acid deposition and the use of road de-icing salts. These factors exert a synergistic effect on the corrosion behavior of auto-body steel and on exterior anodized aluminum automobile trim. 

Auto body corrosion adjacent to stainless steel trim occurs in environments where de-icing salts are used. The effects of acid deposition combined with road salts produces a synergystic effect on the degradation of automobiles. (Photo by Robert... 

The synergistic effect of road salts and acid deposition on corrosion has been investigated [1-4]. The combined effect of the chloride (a film disruptor on metals) and acids (which provide reducible hydrogen ions) can be much worse than the added separate effects. Thus, geographical areas that are subjected to both road salts and acid deposition are likely to be the most corrosive to automobiles. 

Phosphoric acid (H3PO4) solubilizes minerals and thus, is a commonly used adjunct in many formulations. Other acids are also used as cleaning compounds, but these tend to be more corrosive to metal equipment. For example, nitric acid is effective in removing stubborn mineral deposits but tends to prematurely degrade gasket material. 

Guy D. Davis is a staff scientist and group leader of the Surface Sciences Department at Martin Marietta Laboratories. His current research interests include surface-sensitive measurements and their analyses, corrosion of aluminum and its alloys, effects of acid deposition on painted steel, formation and durability of adhesive bonds, and industrial failure analysis. Dr. Davis was the 1986 Distinguished Young Scientist of the Maryland Academy of Sciences. 

A controlled release of inhibitor can also be achieved when there are interactions between the functional groups of the sol-gel matrix and the inhibitor, as schematically shown in Fig. 9.3(c). An additional inhibition effect was revealed when phenylphosphonic acid was introduced into a hybrid sol-gel film containing phenyl groups (Sheffer et al, 2004). The inhibitor becomes entrapped inside the sol-gel matrix due to specific %-% interactions between the phenyl rings. Sol-gel coatings with phenylphosphonic acid deposited on aluminium substrates demonstrate enhanced corrosion protection attributed to the prolonged release of phosphonate ions. 

RW. Lipfert, M. Benarie, and M.L. Daum, Metallic corrosion damage functions for use in environmental assessments, in Proceedings of the Symposia on Corrosion Effects of Acid Deposition and Corrosion of Electronic Materials, Las Vegas, NV, 1985, R Mansfeld, S.R Haagenrud, V. Kucera, RH. Haynie, and J.D. Sinclair (eds.). The Electrochemical Society, Rennington, NJ, vol. 86(6), p. 108 (1986). 

S.E. Haagenrud, J.R. Henriksen, and R. Gram, Dose-response functions and corrosion mapping of a small geographical area. Presented at the Electrochemical Society Symposium on Corrosion Effects of Acid Deposition, Las Vegas, NV, October 1985, Norwegian Institute for Air Research, NILU R 53/85, (1985). 

Exfoliation of susceptible alloys occurs in many outdoor environments, but it develops most rapidly in marine exposure (Fig. 8). The voluminous corrosion products that promote the delamination of the metal form most readily under conditions of intermittent spraying with salt mist or intermittent iimnersion in salt water. The exfoliation effects are stimulated further by acidic deposits (as from gases exhausted by gasoline-burning aircraft engines) and by elevated temperatures. 

In appHcations as hard surface cleaners of stainless steel boilers and process equipment, glycoHc acid and formic acid mixtures are particularly advantageous because of effective removal of operational and preoperational deposits, absence of chlorides, low corrosion, freedom from organic Hon precipitations, economy, and volatile decomposition products. Ammoniated glycoHc acid Hi mixture with citric acid shows exceUent dissolution of the oxides and salts and the corrosion rates are low. 

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