b" Adequate for more than 10 years corrosion aluminum are the most commonly used galvanicprotection for inorganic reducing soils. sacrificial anodes. Insufficientforcorrosionprotectionin The use of cathodic protection using sacrificialhighly reducing organic soils (pH 4) and anodesconnectedtoundergroundmetallicinorganic reducing alkaline soils or cinders structures offers the following advantages:(8 pH 10.5) lasted typically only 3 to 5no external power supply is requiredyears.low cost for anode bags and installation It was also noted, however, that the use ofminimum maintenance costsa galvanized coating significantly reduced Themajorvariablesaresoilmoisturecontent,therateofcorrosionoftheunderlying resistivity of soil and pH.Each of these itemssteel structure once the zinc coating was influencesthefinalselectionofthecathodicdestroyed.Thiswasobservedin protectionsystem.TypicaldesignlifefortheRomanoffsstudywheretheratesof cathodic protection is 10 to 20 years, dependingcorrosionforthepreviouslygalvanized uponthesize,lengthandtypeoftheanodecoatedsteelwerelessthanthecorrosion canister.Aftertheanodeisexhausted,anewrates for never galvanized bare steel. anodeneedstobeinstalled.OtherwisetheActive Control underground steel will begin to corrode.CathodicProtection: Asindicated STEMWALLpreviously,corrosionisanelectrochemical SPREADprocessthatinvolvesaflowofdirect FOOTING UTILITY BRACKETelectrical current from the anodic (corroding) FLOORSLABareasoftheundergroundmetallicstructureinto the electrolyte and back onto the metallicstructureatthecathodic(non-corroding)areas.Insituationswherehelicalpilesor 3' APPROXsteelpiersaretobeplacedinasoilenvironment classified as severely corrosive,Active Control technique of corrosion controlshouldbeused.ThisActiveControltechniqueistermed Active CathodicProtection. 3' TO 6'Thebasicprincipleof ActiveCathodic PILE SHAFTProtection istoapplyanelectricalcurrent MAGNESIUMANODEequal to and opposite to the electrical currentgenerated by the corroding metallic structure,thuseffectivelyeliminatingthecorrosionprocess on the foundation element.SacrificialAnodes: Thesacrificial(galvanic)anodeisattachedtoeachundergroundmetallicstructurebyanelectrical conductor (cable) and the anode isplacedwithinthecommonsoilmedium Figure 2. Active corrosion protection with a magnesium anode.(electrolyte) adjacent to the foundation element. Impressed Current:In areas that have the mostThesacrificialanodeworksbestwhenonlya severecorrosionpotential,requiresalargesmall amount of electrical current is needed for electricalcurrentandinplaceswithhighcorrosion control and/or when the soil resistivity resistanceelectrolytes;animpressedcurrentis low.Anodes are usually installed about three system is generally recommended.This systemfeet below the surface and 3 to 6 feet from the requires a power source, rectifier and a groundsteel subject to corrosion. Magnesium, zinc and bed of impressed current anodes.These systemsECP Technical Design Manual Corrosion Life2021 Earth Contact Products, L.L.C.2021-09 Chapter 8 - Page 153 All rights reserved"