Economics corrosion

The definitions of the terms encountered in discounted cash-flow calculations are taken from the literature.1 3 Discounted cash flow is concerned with the analysis of the value of money as a function of time. The money available at a future date has less value at the present and should be discounted by the interest to present worth (PW). P is the notation for the present sum of money, which should be used in such a manner that it produces a future income more than other forms of investment, irrespective of whether it is used for new equipment or the corrosion mitigation process. Let F be the amount of money available in the future when an investment of P is made. The relation between P and F may be written as  

Corrosion Prevention and Protection Practical Solutions V. S. Sastri, E. Ghali and M. Elboujdaini 2007 John Wiley Sons, Ltd 

The annual cash flow denoted by A and the present value of A discounted by interest rate i is given by  

The P/A ratio is known as the uniform-series present-worth factor. The annual cash flow may be discounted to present worth by multiplication by P/A. Multiplication of present value by A/P gives the amount of annual cash flow. The factors P/F, P/A and A/P for a period of 30 years at interest rates of 6, 8, 10, 12, 15 and 20% for a period of 1-30 years are given in Table 5.1. Depreciation D is an annual tax allowance for the 

N 6% interest factors 10% interest factors 15% interest factors  

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Corrosion economics and corrosion management forms the theme of the fifth chapter. Discounted cash flow calculations, depreciation, the declining balance method, double declining method, modified accelerated cost recovery system and present worth calculation procedures are given, together with examples. In the second part, corrosion management, including the people factor in corrosion failure is briefly presented. Some of the expert systems presently available in the literature are briefly discussed. 

Roberge, P. R. 2000. Handbook of Corrosion Engineering. New York McGraw-HiU. Similar content as Uhlig s, but deals with metals only. Appendices include corrosion economics, chemical compositions of engineering alloys, and thermodynamics data and e-pH diagrams. Available online on Knovel. 

Verink ED. Corrosion economic calculations. In Metals Handbook Corrosion. Metals Park ASM International, 1987 369-74. 

Resistance to initiation of corrosion Economic permanency of corrosion control Application of protective coatings Final appearance Consistency of operation Reduction of vibration. 

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