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MAR -30-99 TUE 06:30 PMC PRO COMPANIES INC FAX NO, 5101 3698 P. 05/07 <br />The accepted criteria indicative of the achievement of cathodic protection on underground <br />steel storage tanks in accordance with NACE International Standard RP0285AS (latest <br />edition), is as follows: <br />NATIONAL ASSOCIATION OF CORROSION ENGINEERS <br />STANDARD RP0295-95 <br />CORROSION CONTROL OF UNDERGROUND STORAGE TANK SYSTEMS <br />BY <br />CATHODIC PROTECTION <br />SECTION 4 <br />4.1 General CRITERIAFOR CATHODIC PROT.ECTiON <br />4.1.1 The purpose of this section is to list criteria for cathodic protection which, when <br />complied with either separately or collectively, will indicate that adequate cathodic <br />protection of metallic LUST system has been achieved. <br />4.1.2 The objective of using cathodic protection is to control the corrosion of UST <br />systems, <br />4.1.3 The selection of a particular criterion depends, in part, on prior experience with <br />similar structures and environments wherein the criterion has been used successfully, <br />4.1.4 The criteria in Section 4.2 were developed through laboratory experiment or were <br />determined empirically by evaluating data obtained from successfblly operated cathodic <br />protection systems. It is not intended that persons responsible for corrosion control be <br />limited to these criteria if it can be demonstrated by other means that the control of <br />corrosion has been achieved. <br />4A.5 Voltage measurement on UST systems are to be made with the reference <br />electrode located on the electrolyte surface as close as possible to the UST system, <br />Consideration must be given to voltage (IR) drops other than those across the <br />structure-olectrolyte boundary, the presence of dissimilar metals, and the influence of <br />Other structures that may interfere with valid interpretation of voltage measurements. <br />Measurements made with a reference electrode located on asphalt pavement or a concrete <br />slab may be in error. <br />NOTE: Consideration is understood to mean the application of sound <br />enghtecring practice in determining the signi6canoe of voltage drops by <br />methods such as: <br />a) Measuring or calculating the voltage drops(s). <br />b) Reviewing the historical performance of the cathodic protection <br />system. <br />c) Evaluating the physical and electrical characteristics of the UST <br />system and its environment, <br />d) Determining whether or not there is physical evidence of corrosion, <br />