Probability Of Corrosion Research Articles

Relationship Between Corrosion and the Biological Sulfur Cycle: A Review

Abstract Sulfur and sulfur compounds can produce pitting, crevice corrosion, dealloying, stress corrosion cracking, and stress-oriented hydrogen-induced cracking of susceptible metals and alloys. Even though the metabolic by-products of the biological sulfur cycle are extremely corrosive, there are no correlations between numbers and types of sulfur-related organisms and the probability or rate of corrosion. Determination of specific mechanisms for corrosion caused by microbiologically mediated oxidation and reduction of sulfur and sulfur compounds is complicated by the variety of potential metabolic/energy sources and by-products; the coexistence of reduced and oxidized sulfur species; competing reactions with inorganic and organic compounds; and the versatility and adaptability of microorganisms in biofilms. The microbial ecology of sulfur-rich environments is poorly understood because of the association of aerobes and anaerobes and the mutualism or succession of heterotrophs to autotrophs. The physical...

Long-Term Performance of Steel Reinforcing Bars in Portland Cement Concrete Incorporating Moderate and High Volumes of ASTM Class F Fly Ash

This paper reports the long-term performance of steel reinforcement in portland cement concrete and concrete incorporating moderate and high volumes of American Society for Testing and Materials (ASTM) Class F fly ash. In 1989, three fly ash concrete mixtures and three control portland cement concrete mixtures were made in Halifax, Canada, and concrete slabs 1,220-by-1,220-by-150 mm thick were cast. Steel reinforcing bars were placed in the slabs with concrete covers of 20 mm, 40 mm, 60 mm, and 80 mm. After 7 days of moist curing and 21 days of air drying, the slabs were ponded with 4% calcium chloride solution. In 1997, 8 years after ponding, half-cell potential measurements were taken to determine the probability of corrosion of the embedded reinforcing bars. Cores were drilled from the slabs for the determination of the compressive strength, resistance of the concrete to chloride ion penetration in accordance with ASTM C 1202, and chloride content at various depths in the slabs. The reinforcing bars were then removed from the slabs for visual inspection. Notwithstanding the results of various tests performed and the relative performance of concrete with or without fly ash after 8 years of exposure to 4% chloride solution, there were no visible signs of any corrosion products on those portions of the steel reinforcing bars that were embedded in the concrete. The only exceptions were the bars with a cover of 20 mm in Slab 5 (25% fly ash, water-cementitious materials ratio = 0.57), and with covers of 20 mm and 40 mm in control concrete Slab 6 (water-cement ratio = 0.57) that showed some evidence of corrosion. In general, the concrete incorporating moderate and high volumes of fly ash showed superior resistance to the penetration of chloride ions compared to the control concrete.

Localized Corrosion Probability in Stainless Steels After Cathodic Protection in Seawater

Abstract Growth of calcareous deposits on stainless steels (SS) exposed to seawater under cathodic protection (CP) conditions was examined. CP was performed by galvanic coupling with iron, zinc, or...

Monitoring of concrete structures with respect to rebar corrosion

From security aspects as well as economic reasons it is desirable to localize reinforcement corrosion at an early stage and with non-destructive techniques in order to initiate the necessary rehabilitation measures in time. The potential mapping technique, i.e. measuring half-cell potentials at concrete surfaces with reference electrodes, is a helpful tool to obtain information about the actual state of rebar corrosion. The potential measurement can be modified by additionally applying a short anodic pulse by means of a small counter electrode and a galvanostat. In some cases this technique leads to noticeable improvements with respect to information about the probability of corrosion. The fundamentals of the two kinds of potential measurement techniques are explained and results obtained at different types of structures are described.

Probability of corrosion induced cracking in reinforced concrete

A probabilistic approach to corrosion induced cracking in reinforced concrete was investigated. Hydraulic pressurization at the reinforcement/concrete interface was used to simulate corrosion of reinforcement and cause fracture. The failure pressure data was analysed statistically and found to have right hand skew. Correlation between failure pressure and visual observations of fracture surfaces suggested a possible change in failure mechanism depending on the presence of voids near the reinforcement. The failure pressure distributions were analysed to determine whether Weibull statistics could provide an adequate description. The effects of variables such as toughness, flaw size, corrosion products and corrosion rate on the shape of failure probability-time relationships were predicted.

Application of Extreme Value Statistics to Corrosion.

Application of extreme value statistics to corrosion is reviewed. It is emphasized that the concept of corrosion probability is important for a quantitative evaluation of corrosion failure and its prediction, especially for localized corrosion. Extreme value statistics is quite useful for assessing the maximum pit depth and/or the minimum time for crack generation. The maximum pit depth depending on the surface area can be evaluated by using the Gumbel distribution with the concept of return period. A standardized procedure is proposed for estimating the maximum pit depth. Examples of corrosion failure analysis using extreme value statistics, which were reported mainly in Japan, are shown. Accumulated experiences suggest that an appropriate classification of data based on the corrosion mechanism is required before applying extreme value analysis.

腐食確率

腐食確率

Cathodic Protection Used to Control Corrosion of SERVICE STATION UNDERGROUND EQUIPMENT

Abstract Explains economic importance of controlling corrosion of service station underground equipment. Describes methods of determining corrosion probabilities, lists coatings suggested for service station use and explains importance of soil resistivity. Shows how current requirements are determined for cathodic protection of underground storage tanks. Describes protection by sacrificial anodes and by rectifiers. Also gives tabular data on economics of cathodic protection. Illustrations show typical installations. Graphs give information for determining anode currents required. 3.2.1

Anodic polarization as a possible rapid method of deciding whether a given solution is corrosive or inhibitive

AbstractAnodic polarization curves have been obtained with twelve systems of mixed corrosive and inhibitive ions and it has been found that when the results are compared with total immersion tests, the corrosive or inhibitive nature of the solutions could be estimated from the nature of the polarization curves, with only one exception (NaNO2 + NaCl).In several cases corrosion occurred in the immersion tests when the polarization curves indicated that the solution was just inhibitive, but the borderline between corrosion and passivity is not clear cut and there are reasons for believing that with solutions in the borderline region this method has a slight bias towards passivity.The probability of corrosion increases with the size of the specimen and is affected by shape, i.e. by the presence of crevices where the inhibitor may become exhausted.When modified this method may form the basis of an accelerated test.

Reactivity of Freshly Formed Steel Surfaces

PRINCE1 has observed that a freshly sheared steel surface rusts far quicker than would be expected at ordinary temperatures. Whether or not it is always legitimate, in statistically distributed events, to draw conclusions from isolated observations, recorded facts support his statement in the present case. The corrosion probability of a freshly scraped surface is higher than that of a surface exposed to air ; statistical studies by Hears2 have shown that the probability number for rusting at scratch lines traced on iron, and, after exposure to air, covered with 0.07 M sodium bicarbonate, declines steadily with the duration of exposure.

Corrosion Probability

Corrosion Probability