Assessment corrosivity

FlOiei Evaluation of techniques for assessing corrosion cracking In dissimilar metal welds Dr D.R. Tice AEA Technology... 

Measurements for Assessing Corrosion Protection of Well Casings... 

Pourbaix, M., A Comparative Review of Electrochemical Methods of Assessing Corrosion and the Behavior in Practice of Corrodible Material , Corros. Sci., 5, 67 (1965)... 

In considering the corrosion of magnesium and its alloys it is important to examine the methods available for assessing corrosion tendencies and particularly those known as accelerated tests. Tests carried out by immersion in salt water or by spraying specimens regularly with sea-water are worthless as a means of determining the resistance of magnesium alloys under any other than the particular test conditions. Extrapolation to less corrosive conditions is not valid and even the assessment of the value of protective measures by such means is hardly possible. The reason is to be found in the fact that corrosion behaviour is directly related to the formation of insoluble... 

Infrared Methods Commercial instrumentation for recording infrared radiation has been available for some years and has been explored by the electrical power industry in the UK for assessing corrosion in boiler tubes at power-station shut-down. An external heal source is played onto the outside of boiler tubes at the same time as cold water is circulated inside the tubes. Hot spots due to poor heat conductivity caused by excessive corrosion product indicated areas of high corrosion. 

However, in the same way that it is unwise for water treaters to rely only on metal coupons when assessing corrosion rates, or only on dip-slides when identifying microbiological infections, information obtained from LSI and SI tools should always be used in conjunction with other sources of related and relevant information. Simple predictive indices should not be used as sole criteria for water management action or change, nor an overreliance placed on them. To obtain high cycles of concentration (COC) yet balance the increased risk of deposition, the use of ion-association predictive modeling is preferred to LSI and SI. 

Niederhauser et al ° used the alternative approach of coating the molybdenum disulphide in a sputtered coating with PTFE to protect it from attack by moisture. They found that there was some reduction in corrosion of a steel substrate, although a greater reduction was obtained when the coating was sputtered onto a rhodium interlayer. Zhai et al also reported some improvement in the stability of a composite plating when cerium was incorporated to coat the molybdenum disulphide and reduce moisture attack, but they did not directly assess corrosion resistance. 

Mass accumulation probes as the name suggests, are used to obtain a deposit that can be weighed, i.e. a direct measurement of the fouling per unit area of probe for given conditions. The technique has also been used to assess corrosion under the conditions within a combustion space. 

Figure 16.1 Example of integrated methodology of inspection for assessing corrosion of...

R. Myrdal, Evaluation of electrochemical techniques for assessing corrosion of steel in concrete", dissertation for the degree of Doctor Scientarium, University of Oslo, 1997. 

Finland and Sweden Finland conducted a study of the cost of corrosion in 1965, and the cost of corrosion was estimated to be between 150 and 200 million markka (U.S. 47 million and U.S. 62 million) for the year 1965. Linder-borg referred to these losses in the paper describing factors that must be taken into account in assessing corrosion cost (11) to Finland. 

Step 3 Develop and assess corrosion control alternatives... 

B.S. Skerry, C.H. Simpson, Accelerated test method for assessing corrosion and weathering of paints for atmospheric corrosion control. Corrosion 49 (1993) 663—674. 

An example of such is shown in Figure 4.23 where a tubercle-like shape has been formed without the involvement of bacteria versus lOB-induced tubercles. These are, obviously, very crucial matters that should be a matter of concern while assessing corrosion cases. 

R. Javaherdashti, E.G. Marhamati. A computerized model incorporating MIC factors to assess corrosion in pipelines. Materials Performance, Vol. 44, No. 1, pp. 56-59, January 2005. 

The final chapter discusses future developments. As materials science, computer technology, electronics and other disciplines advance, new methods for assessing corrosion are becoming available. The author speculates about what will be on offer and perhaps more importantly what we need to efficiently assess and repair corrosion damage on our fixed infrastructure in the future. 

Chapter 4 dealt with the different test methods available for assessing corrosion related properties of reinforced concrete. Most of the techniques are applied with hand-held battery operated equipment and a one off reading is taken. In some cases such as cover meter measurements that reading will not change. In others, such as concrete resistivity, corrosion rate or corrosion potential (reference electrode potential) it will change as aggressive agents in the environment move into the concrete and lead to or accelerate corrosion. 

Since molten salts are very reactive, due especially to the appearance of temperature in the exponential part of rate equations, it is unlikely that corrosion will be kinetically inhibited if thermodynamically predicted, as is often encountered in aqueous solutions. Moreover, when assessing corrosion possibilities, the whole system including container materials needs to be considered, since the latter are rarely inert in contact with melts. 

The use of spot hydrogen flux measurements in assessing corrosion and crack risk in refinery applications... 

Corrosion test specimens are used to evaluate average corrosion rate over the exposure period and eire also useful for assessment of crevice corrosion, pitting, and end grain attack, and may be used for metallographic examination of the corrosion test specimen or analysis of any deposits. Special corrosion test specimens may be prepared with welds to assess corrosion problems particular to weld material or heat affected zones. SCC may be monitored with specially mounted and loaded corrosion test specimens. 

Arup, H., Sorensen, B., Frederiksen, J., and Thaulow, N., The Rapid Chloride Permeation Test— An Assessment, Corrosion/93, Paper 334, NACE, New Orleans, March 1993. 

Weight loss corrosion rates, which represent an average of corrosion over the test period, are useless from a predictive point of view, but are often used in conjunction with other measurements for quality assessments. Corrosion kinetics can be measured in different ways. Most favored are electrochemical techniques. They are, however, contrary to common belief, indirect techniques and must be properly calibrated and interpreted to be useful. If corrosion products are soluble in solution (as, for instance, iron carbonate), the buildup of such in solution can be used to monitor how corrosion progresses. Hydrogen, a byproduct of anaerobic corrosion, can also be used to monitor kinetics. Less common, but equally direct, are methods that use the removal of radioactivity from irradiated surfaces. Kinetic measurements have also been carried out with electrical resistance probes. As a general principle, no one method is in itself without some problems and should, therefore, always... 

Depth of attack can be used to assess corrosion damage in MMCs. It may be more difficult, however, to assess the penetration depth in MMCs compared to that in monolithic metals because reinforcement constituents that are left in relief can prevent a depth gage x>m contacting the matrix surface, and thus, prevent the true depth of penetration from being measured. In particulate MMCs, the interference may be attenuated since reinforcement particles are free to detach from the matrix as they are undercut by corrosion. When reinforcements interfere with mechanical measurements, depth of penetration can be assessed metal-lographicaUy. Samples may be mounted and polished, and penetration measurements can be made with a microscope and a calibrated eyepiece. Details for determining penetration depth are available in ASTM G 46, Recommended Practice for Examination and Evaluation of Pitting Corrosion. 

Corrosion tests are performed for selection or qualification of materials (including materials to be used for repairs or replacements), for monitoring (to assess corrosion or to track process controls such as water treatments), or to supplement and assist with failure anedyses. 

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