tailieunhanh - Handbook of Corrosion Engineering Episode 1 Part 4

Tham khảo tài liệu 'handbook of corrosion engineering episode 1 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 70 Chapter Two parameters humidity SO2 etc Corrosion measurements Corrosivity Classification Correlation with historical performance data Corrosion Rate Guidelines Coating Performance Guidelines Materials Selection and Corrosion Control Measures Figure Two fundamental approaches to classifying atmospheric corrosivity. TABLE List of ISO Standards Related to Atmospheric Corrosion ISO standard Title ISO 9223 ISO 9224 ISO 9225 Classification of the Corrosivity of Atmospheres Guiding Values for the Corrosivity Categories of Atmospheres Aggressivity of Atmospheres Methods of Measurement of Pollution Data ISO 9226 Corrosivity of Atmospheres Methods of Determination of Corrosion Rates of Standard Specimens for the Evaluation of Corrosivity Environments 71 Industrial pollution by SO2. Two types of units are used Concentration -m 3 PC Pc 40 P1 40 PC s 90 p2 90 Pc P3 Deposition rate mg -m 2-day P Pd s 35 Pi 35 PD 80 P2 80 PD P3 Corrosion rate categories. Two types of corrosion rates are predicted Category Short-term g-m 2-year 1 Long-term m-year 1 C1 CR 10 CR C2 10 CR 200 CR c3 200 CR 400 CR 6 c4 400 CR 650 6 CR 20 C5 650 CR 20 CR The TOW categorization is presented in Table and the sulfur dioxide and chloride classifications are presented in Table . TOW values can be measured directly with sensors or the ISO definition of TOW as the number of hours that the relative humidity exceeds 80 percent and the temperature exceeds 0 C can be used. The methods for determining atmospheric sulfur dioxide and chloride deposition rates are described more fully in the relevant standards Table . Following the categorization of the three key variables the applicable ISO corrosivity category can be determined using the appropriate ISO chart Table . Different corrosivity categories apply to different types of metal. As the final step in the ISO procedure the rate of atmospheric corrosion can be estimated for the determined corrosivity category. Table .