b"in weight of steel per year is estimated to be 1.042. Estimated Life Galvanize Loss: Estimate oz/ft 2per year.theaveragelifeofgalvanizedcoatingatthe Using Equation 2, the corrosion life for the steellocation that has the lowest soil resistivity.Use tube is determined.Equation 1 introduced in Chapter 8 to estimatethe average life of the galvanized coating. CL P= W S-10% / K CEquation 1 - Corrosion Life Zinc: Where:CLP = Life expectancy of steel tube (years)CL G= G / [0.25 - 0.12 log 10(R/150)] W S-10%= 19.6 oz/ft 2(Weight loss of steel pier)Where: K C= 1.04 oz/ft 2(Corrosion loss per year.)CL G= Weight loss (oz/ft 2 )/yearG = 1.7 oz/ft 2 (HDGASTM A123 Gr.75) CL P= 19.6/ 1.04 = 18.8 yearsR = 750 ohm-cm (Lowest soil resistivity)Determine CL Gusing Equation 1:CORROSION POTENTIAL ESTIMATING GRAPHCL G= 1.7 / [0.25 - 0.12 log 10(750/150)] UNDERGROUND BARE STEEL STRUCTURESCORROSION= 1.7 / [0.250.12 log 105.0]POTENTIAL= 1.7 / [0.250.12 (0.699) 100,000= 1.7 / 0.166 70,000 UNLIKELYCL G= 10.2 years 50,000 ALL pH's3.Corrosion Life EstimatedSteel Loss: 3 pH 6 SLIGHTTheformulaforestimatingaveragetimefor 20,00010% loss of wall thickness of steel tube is given10,000in Equation 2 from Chapter 8: 7000 MILDEquation 2 - Corrosion Life Steel Shaft: 5000RESISTIVITY (ohm-cm)CL P= W S-10% / K C MODERATEWhere: 2000CLP = Life expectancy of steel tube (years)W S-10%= 10% pile weight loss(oz/ft 2 ) 1000700K C = Corrosion loss per year - oz/ft 2 500 W S-10% istheamountofsteellossequal to SEVERE10%ofthewallthicknessofa3-1/2inch 200 pH 4.5diameter with 0.300 inch wall thickness must pH 12 pH 10.5first be determined. 1007050pH = 5 pH = 6 pH = 7 pH = 8 pH = 9 pH = 10Equation 3: 03 0.25 0.5 0.75 1.0 1.25 1.5 1.75 2.0 2.25 2.5W S-10%= 10% [t/12] x 489.6 lb/ftx 16 oz/lb LOSS IN WEIGHT BY CORROSION PER YEAR (oz./sq. ft.)Where: t = Wall thickness of shaft - inches Graph 3.The pile shaft used for this example is a TAF- 4.Determinethecorrosionlifeofthepile:350 tubular shaft, which is 3-1/2 inches diameter Thetimeforthegalvanizedcoatingtocorrodewith 0.300 inch wall thickness.Using Equation and for ten percent corrosion loss of the steel is3, the value of W S-10% is calculated: the average corrosion life expectancy of the steelW S-10%= 0.10 x [0.300/12] x 489.6 x 16W S-10%= 19.6 oz/ft 2 pile shaft when installed at this job site.Next,thecorrosionlossrate(K C )mustbeLife = CL G+ CL P= 10.2 + 18.8 = 29 yearsdetermined using Graph 3 presented in Chapter Baseduponthedataandtheassumptions,the8.Itisreproducedatrightforreference. analysissuggeststhattheTorqueAnchor Knowingthatthelowestresistivityrelatesto helical pile shafts specified for this project willhighest rate of corrosion, locate 750 ohm-cm on support the design load, plus a full 2.0 factor ofthe left axis.Reading horizontally to the right safety with no loss in capacity for an estimatedfindthecurvedlinethatrepresentspH=8.0. average corrosion life exceeding 29 years.Readingdirectlydownward,thecorrosionloss Corrosion Life= 29+ years*ECP Technical Design ManualCorrosion Life Design Examples2021 Earth Contact Products, L.L.C.2021-09 Chapter 9Page 161 All rights reserved"