Api rp 652 2014 (2016) (american petroleum institute)

RP 652 e4 fm Linings of Aboveground Petroleum Storage Tank Bottoms API RECOMMENDED PRACTICE 652 FOURTH EDITION, SEPTEMBER 2014 ERRATA 1, AUGUST 2016 Special Notes API publications necessarily address[.]

Linings of Aboveground Petroleum Storage Tank Bottoms

API RECOMMENDED PRACTICE 652

FOURTH EDITION, SEPTEMBER 2014

ERRATA 1, AUGUST 2016

API publications necessarily address problems of a general nature With respect to particular circumstances, local,state, and federal laws and regulations should be reviewed.

Neither API nor any of API's employees, subcontractors, consultants, committees, or other assignees make anywarranty or representation, either express or implied, with respect to the accuracy, completeness, or usefulness of theinformation contained herein, or assume any liability or responsibility for any use, or the results of such use, of anyinformation or process disclosed in this publication Neither API nor any of API's employees, subcontractors,consultants, or other assignees represent that use of this publication would not infringe upon privately owned rights.API publications may be used by anyone desiring to do so Every effort has been made by the Institute to assure theaccuracy and reliability of the data contained in them; however, the Institute makes no representation, warranty, orguarantee in connection with this publication and hereby expressly disclaims any liability or responsibility for loss ordamage resulting from its use or for the violation of any authorities having jurisdiction with which this publication mayconflict

API publications are published to facilitate the broad availability of proven, sound engineering and operatingpractices These publications are not intended to obviate the need for applying sound engineering judgmentregarding when and where these publications should be utilized The formulation and publication of API publications

is not intended in any way to inhibit anyone from using any other practices

Any manufacturer marking equipment or materials in conformance with the marking requirements of an API standard

is solely responsible for complying with all the applicable requirements of that standard API does not represent,warrant, or guarantee that such products do in fact conform to the applicable API standard

Users of this Recommended Practice should not rely exclusively on the information contained in this document.Sound business, scientific, engineering, and safety judgment should be used in employing the information containedherein

API is not undertaking to meet the duties of employers, manufacturers, or suppliers to warn and properly train andequip their employees, and others exposed, concerning health and safety risks and precautions, nor undertaking theirobligations to comply with authorities having jurisdiction

Information concerning safety and health risks and proper precautions with respect to particular materials andconditions should be obtained from the employer, the manufacturer or supplier of that material, or the material safetydata sheet

Where applicable, authorities having jurisdiction should be consulted

Work sites and equipment operations may differ Users are solely responsible for assessing their specific equipmentand premises in determining the appropriateness of applying the Standard At all times users should employ soundbusiness, scientific, engineering, and judgment safety when using this Standard

All rights reserved No part of this work may be reproduced, translated, stored in a retrieval system, or transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior written permission from the publisher Contact the

Publisher, API Publishing Services, 1220 L Street, NW, Washington, DC 20005

Copyright © 2014 American Petroleum Institute

Nothing contained in any API publication is to be construed as granting any right, by implication or otherwise, for themanufacture, sale, or use of any method, apparatus, or product covered by letters patent Neither should anythingcontained in the publication be construed as insuring anyone against liability for infringement of letters patent.Shall: As used in a standard, “shall” denotes a minimum requirement in order to conform to the specification.

Should: As used in a standard, “should” denotes a recommendation or that which is advised but not required in order

to conform to the specification

This document was produced under API standardization procedures that ensure appropriate notification andparticipation in the developmental process and is designated as an API standard Questions concerning theinterpretation of the content of this publication or comments and questions concerning the procedures under whichthis publication was developed should be directed in writing to the Director of Standards, American PetroleumInstitute, 1220 L Street, NW, Washington, DC 20005 Requests for permission to reproduce or translate all or any part

of the material published herein should also be addressed to the director

Generally, API standards are reviewed and revised, reaffirmed, or withdrawn at least every five years A one-timeextension of up to two years may be added to this review cycle Status of the publication can be ascertained from theAPI Standards Department, telephone (202) 682-8000 A catalog of API publications and materials is publishedannually by API, 1220 L Street, NW, Washington, DC 20005

Suggested revisions are invited and should be submitted to the Standards Department, API, 1220 L Street, NW,Washington, DC 20005, standards@api.org

iii

1 Scope 1

2 Normative References 1

2.1 Codes, Standards, and Specifications 1

2.2 Other References 3

3 Terms and Definitions 4

4 Corrosion Mechanisms 7

4.1 General 7

4.2 Chemical Corrosion 7

4.3 Concentration Cell Corrosion 8

4.4 Galvanic Cell Corrosion 8

4.5 Microbiologically Influenced Corrosion (MIC) 8

4.6 Erosion-Corrosion 8

4.7 Fretting-Related Corrosion 9

5 Determination of the Need for Tank Bottom Lining 9

5.1 General 9

5.2 Linings for Corrosion Prevention 9

5.3 Tank Corrosion History 10

5.4 Tank Foundation 10

6 Tank Bottom Lining Selection 10

6.1 General 10

6.2 Thin-film Tank Bottom Linings 11

6.3 Thick-film, Unreinforced Linings 12

6.4 Thick-film Reinforced Linings 13

6.5 Circumstances Affecting Lining Selection 14

7 Surface Preparation 15

7.1 General 15

7.2 Pre-cleaning 16

7.3 Bottom Repair and Weld Preparation 16

7.4 Surface Cleanliness 17

7.5 Surface Profile or Anchor Pattern 17

7.6 Air and Abrasive Cleanliness 17

7.7 Removal of Salts 17

7.8 Removal of Dust 17

8 Lining Application 17

8.1 General 17

8.2 Guidelines for Lining Application 18

8.3 Temperature and Humidity Control 18

8.4 Lining Thickness 18

8.5 Lining Curing 18

v

9 Inspection 19

9.1 General 19

9.2 Qualification of Inspection Personnel 19

9.3 Recommended Inspection Parameters 19

10 Evaluation and Repair of Existing Linings 20

10.1 General 20

10.2 Evaluation Methods 20

10.3 Evaluation Criteria for Linings 20

10.4 Evaluating Serviceability of Existing Linings 21

10.5 Determining the Cause of Lining Degradation/Failure 21

10.6 Lining Repair and Replacement 21

11 Maximizing Lining Service Life by Proper Material Selection and Specification 22

11.1 General 22

11.2 Lining Material Selection 22

11.3 Written Specification 23

12 Health, Safety, and Environmental 23

12.1 General 23

12.2 Tank Entry 24

12.3 Surface Preparation and Lining Application 24

12.4 Manufacturer’s Material Safety Data Sheets 24

1 Scope

This recommended practice (RP) provides guidance on achieving effective corrosion control in aboveground storagetanks by application of tank bottom linings It contains information pertinent to the selection of lining materials, surfacepreparation, lining application, cure, and inspection of tank bottom linings for existing and new storage tanks In manycases, tank bottom linings have proven to be an effective method of preventing internal corrosion of steel tankbottoms

The intent of this RP is to provide information and guidance specific to aboveground steel storage tanks inhydrocarbon service Certain practices recommended herein may also be applicable to tanks in other services This

RP is intended to serve only as a guide Detailed tank bottom lining specifications are not included

This RP does not designate specific tank bottom linings for every situation because of the wide variety of serviceenvironments

NACE No.10/SSPC-PA 6 and NACE No 11/SSPC-PA 8 are industry consensus standards for installation of linings

on tank floors and vessels They are written in compulsory language and contain specific criteria intended for use bypersons who provide written specifications for tank and vessel linings These documents should be givenconsideration when designing and installing a lining system for steel bottom tanks

2 Normative References

2.1 Codes, Standards, and Specifications

The following referenced documents are indispensable for the application of this document For dated references,only the edition cited applies For undated references, the latest edition of the referenced document (including anyamendments) applies

API Recommended Practice 575, Inspection of Atmospheric and Low-Pressure Storage Tanks

API Standard 620, Design and Construction of Large, Welded, Low-Pressure Storage Tanks

API Standard 650, Welded Tanks for Oil Storage

API Recommended Practice 651, Cathodic Protection of Aboveground Petroleum Storage Tanks

API Standard 653, Tank Inspection, Repair, Alteration, and Reconstruction

API Standard 2015, Requirements for Safe Entry and Cleaning of Petroleum Storage Tanks

API Recommended Practice 2016, Guidelines and Procedures for Entering and Cleaning Petroleum Storage Tanks

ASTM D25831, Standard Test Method for Indentation Hardness of Rigid Plastics by Means of a Barcol Impressor ASTM D4414, Standard Practice for Measurement of Wet Film Thickness by Notch Gages

1 ASTM International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428, www.astm.org

ASTM D4417, Standard Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel

ASTM D4940, Standard Test Method for Conductimetric Analysis of Water Soluble Ionic Contamination of Blasting

Abrasives

ASTM D5402, Standard Practice for Assessing the Solvent Resistance of Organic Coatings Using Solvent Rubs ASTM E96, Standard Test Methods for Water Vapor Transmission of Materials

ASTM G9, Standard Test Method for Water Penetration into Pipeline Coatings

DSTAN 80-972, Paint System, Medium Build for the Interior of Bulk Fuel Tanks and Fittings

ISO Standard 8502-33, Preparation of steel substrates before application of paints and related products – Tests for

the assessment of surface cleanliness—Part 3: Assessment of dust on steel surfaces prepared for painting (pressure-sensitive tape method)

MIL-PRF-23236D4, Performance Specification: Coating Systems for Ship Structures

NACE 375195, Corrosion Data Survey—Metals Section

NACE TM0174, Laboratory Methods for the Evaluation of Protective Coatings and Lining Materials on Metallic

Substrates in Immersion Service

NACE RP0188, Discontinuity (Holiday) Testing of New Protective Coatings on Conductive Substrates

NACE RP0178, Fabrication Details, Surface Finish Requirements, and Proper Design Considerations for Tanks and

Vessels to be Lined for Immersion Service

NACE RP0287, Field Measurement of Surface Profile of Abrasive Blast-Cleaned Steel Surfaces Using a Replica

Tape

NACE No 1/SSPC-SP 5, White Metal Blast Cleaning

NACE No 2/SSPC-SP 10, Near-White Metal Blast Cleaning

NACE No 5/SSPC-SP 12, Joint Surface Preparation Standard: Surface Preparation and Cleaning of Metals by

Waterjetting Prior to Recoating

NACE No 10/SSPC-PA 6, Fiberglass-Reinforced Plastic (FRP), Linings Applied to Bottoms of Carbon Steel

Aboveground Storage Tanks

NACE No 11/SSPC-PA 8, Thin-Film Organic Linings Applied in New Carbon Steel Process Vessels

NACE 6A192/SSPC-TR 3, Dehumidification and Temperature Control During Surface Preparation, Application, and

Curing for Coatings/Linings of Steel Tanks, Vessels, and Other Enclosed Spaces

2 UK Defence Standardization, Room 1138, Kentigern House, 65 Brown Street, Glasgow, G2 8EX www.dstan.mod.uk

3 International Organization for Standardization, 1, ch de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland,www.iso.org

4 Available online at http://assist.daps.dla.mil/quicksearch/ or http://assist.daps.dla.mil or from the Standardization DocumentOrder Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094

5 NACE International (formerly the National Association of Corrosion Engineers), 1440 South Creek Drive, Houston, Texas77084-4906, www.nace.org

OSHA 29 CFR6, Part 1910—Occupational Safety and Health Standards by OSHA

1910.94, Ventilation

1910.132, Personal Protective Equipment, General Requirements

1910.134, Respiratory Protection

1910.146, Permit-Required Confined Spaces

1910.147, The Control of Hazardous Energy (Lockout/Tagout)

1910.1000, Air Contaminants

1910.1200, Hazard Communication

1926.354, Welding, Cutting, and Heating in way of Preservative Coatings

1926.62, Lead

OSHA Publ 22547, Training Requirements in OSHA Standards and Training Guidelines

SSPC Guide 158, Field Methods for Extraction and Analysis of Soluble Salts on Steel and Other Nonporous

Substrates

SSPC-PA 1, Shop, Field, and Maintenance Painting of Steel

SSPC-PA 2, Procedure for Determining Conformance to Dry Coating Thickness Requirements

SSPC-PA 10, Guide to Specifying and Testing Coatings Conforming to Volatile Organice Compound (VOC) Content

Requirements

SSPC-SP 1, Solvent Cleaning

SSPC-SP 11, Power Tool Cleaning to Bare Metal

SSPC-VIS 1, Guide and Reference Photographs for Steel Surfaces Prepared by Dry Abrasive Blast Cleaning

UFGS 09 97 13.159, Epoxy/Fluoropolyurethane Interior Coating of Welded Steel Petroleum Fuel Tanks

2.2 Other References

Although not cited in the text, these publications may be of interest or contain related material

API Recommended Practice 2009, Safe Welding, Cutting and Hot Work Practices in the Petroleum & Petrochemical

Industries

6 The Code of Federal Regulations is available from the U.S Government Printing Office, Washington, DC 20402, www.gpo.gov

7 U.S Department of Labor, Occupational Safety and Health Administration, 200 Constitution Avenue, NW, Washington, DC

20210, www.osha.gov

8 The Society for Protective Coatings, 40 24th Street, 6th Floor, Pittsburgh, Pennsylvania 15222, www.sspc.org

9 National Institute of Building Sciences (NIBS), 1090 Vermont Avenue NW, Suite 700, Washington, DC 20005, www.wbdg.org/ccb/ccb.php

API Publication 2207, Preparing Tank Bottoms for Hot Work

ACGIH10, Threshold Limit Values (TLVs®) and Biological Exposure Indices (BEIs®)

NACE Handbook 1, Forms of Corrosion—Recognition and Prevention, Vol 1 & 2

SSPC-AB 1, Mineral and Slag Abrasives

SSPC-AB 2, Cleanliness of Recycled Ferrous Metallic Abrasive

SSPC-AB 3, Ferrous Metallic Abrasive

3 Terms and Definitions

For the purposes of this document, the following definitions apply

3.1

aboveground storage tank

A stationary container, usually cylindrical in shape, consisting of a metallic roof, shell, bottom, and support structurewhere more than 90 % of the tank volume is above surface grade

The electrode of an electrolytic cell in which oxidation is the principal reaction

NOTE Electrons flow away from the anode in the external circuit It is usually the electrode where corrosion occurs and metalions enter solution

A corrosion control system in which the metal to be protected is made to serve as a cathode, either by the deliberate

establishment of a galvanic cell or by impressed current (See anode and cathode.)

10 American Conference of Governmental Industrial Hygienists, 1330 Kemper Meadow Drive, Cincinnati, Ohio 45240-1634,www.acgih.com

coal tar epoxy

A combination of epoxy, curing agent, and tar products which give a very water resistant film

differential aeration cell

oxygen concentration cell

A concentration cell caused by differences in oxygen concentration along the surface of a metal in an electrolyte

(See concentration cell.)

3.14

electrochemical cell

An electrochemical system consisting of an anode and a cathode in metallic contact and immersed in an electrolyte

NOTE The anode and cathode may be different metals or dissimilar areas on the same metal surface

One one-thousandth of an inch (0.001 in.)

NOTE One mil = 25.4 µm; it is common practice to use 1 mil = 25 µm

A resin of the phenol formaldehyde type

NOTE Phenolic and novolac epoxies tend to be more chemically resistant

3.23

primer

First complete coat applied to the prepared surface

NOTE Holding primers are often used in tank linings when operational issues require daily coating of the blasted surface

vinyl ester

A chemically resistant resin frequently used in flake coatings as well as in the fiberglass reinforced thick-film systems

NOTE This product contains styrene, which is on the HAPS list and is a carcinogen

4 Corrosion Mechanisms

4.1 General

Corrosion rates of carbon steel in various hydrocarbons have been determined and are given in many reference texts

such as NACE Corrosion Data Survey–Metals Section These rates apply only if there are no accelerating

mechanisms For example, corrosion would not be expected in ambient temperature crude oil or product service with

no water present; however, corrosion may occur when a layer of water settles to the bottom of a crude oil,intermediate product, or finished product storage tank This water, which may enter the tank with the product, throughthe seals, or during “breathing” of the tank, often contains corrosive compounds For example, crude oil may containsalt water and sediment that settles out on the bottoms of storage tanks Chlorides and other soluble salts contained

in the water may provide a strong electrolyte that can promote corrosion The common mechanisms of internal tankbottom corrosion include:

a) chemical corrosion;

b) concentration cell corrosion;

c) galvanic cell corrosion;

d) Microbiologically Influenced Corrosion (MIC);

4.3 Concentration Cell Corrosion

Concentration cell corrosion may occur when a surface deposit, mill scale, or crevice creates a localized area of loweroxygen concentration The area under a surface deposit may be penetrated by a thin layer of electrolyte, which soonbecomes depleted of oxygen The difference in oxygen concentration between the inaccessible area and the bulkelectrolyte creates a galvanic cell, with the contact area of the surface deposit being anodic to the surrounding tankplate Concentration cell corrosion will cause pitting and may result in significant localized metal loss Pitting of a baresteel tank bottom may occur at a rate as high as 80 mils (2.0 mm) per year

4.4 Galvanic Cell Corrosion

Hot-rolled carbon steel, typically used for the construction of petroleum storage tanks, is covered with a thin layer ofoxide called mill scale, which is cathodic to the base steel In the presence of a corrodent (such as dissolved oxygen)and an electrolyte, a galvanic corrosion couple forms at breaks in the mill scale Accelerated pitting corrosion of thesteel at breaks in the mill scale can result Mill scale may be removed from both sides of the tank bottom plate byabrasive blast cleaning or by pickling, but removal of mill scale from the underside of the steel bottom is notcommonly done Removal of mill scale from the underside of new steel bottoms may be considered in an effort topromote a more uniform corrosion and minimize accelerated pitting corrosion that may occur

In some cases, welding can produce large differences in the microstructure of a steel bottom plate resulting in a

built-in galvanic couple In the presence of a corrodent and an electrolyte, preferential corrosion can occur at the affected zones (HAZ) of the base metal near the welds This type of corrosion can cause significant localized metalloss

heat-4.5 Microbiologically Influenced Corrosion (MIC)

Bacteria [e.g sulfate reducing bacteria (SRB) and acid producing bacteria (APB)] are widespread in the petroleumindustry The role of bacteria in corrosion is universally recognized but the mechanisms are not well understood.Generally, the effect of bacteria on the corrosion of bare steel tank bottoms is negligible In some cases, however,severe corrosion has been attributed to MIC The bacteria colonies form deposits on the steel that may provide aneffective barrier to the diffusion of dissolved oxygen Thus, the mere physical presence of bacterial deposits canpromote aggressive pitting corrosion by the concentration cell mechanism described in 4.3

The metabolism of bacteria is important with regard to the corrosion of storage tank bottoms Most bacteria found inthe petroleum industry are strict anaerobes that do not proliferate in the presence of oxygen; however, the densebacterial colonies create a local anaerobic condition, even if some oxygen is available By creating the local anaerobiccondition, the bacteria can stay alive in the presence of oxygen, even though the colonies do not expand In the case

of SRB, colonies derive energy principally from the reduction of sulfates to sulfide, and this metabolic end product iscorrosive to steel Moreover, the iron sulfide corrosion product is cathodic to the base steel and may promoteaccelerated pitting corrosion by a galvanic mechanism, as described in 4.4, if dissolved oxygen is available as acorrodent This type of corrosion can often be found in tanks containing diesel or fuel oils

4.6 Erosion-Corrosion

Erosion-corrosion may occur in wastewater treating or mixing tanks where soil or small abrasive aggregate ispresent To a lesser extent, erosion-corrosion can also occur at tank mixers in crude oil storage tanks A watertreatment tank blends chemicals into contaminated water to break any emulsions of oil and water Agitation mayincrease corrosion by delivering more corrodent, such as dissolved oxygen, from the bulk of the stored product to thesurface of the tank steel Turbulence also moves any fine aggregate that is present, creating an abrasiveenvironment in which adherent, semi-protective corrosion products can be dislodged, exposing the underlying steel

to the corrosive environment Severe erosion conditions may scour the base metal directly Erosion-corrosion causeshighly localized metal loss in a well-defined pattern Erosion corrosion may be found at tank inlets and outlets whereproduct flow occurs

4.7 Fretting-Related Corrosion

Fretting-related corrosion may occur in hydrocarbon service on the bottoms of external floating roof tanks When thetank is emptied, the floating roof is typically supported on roof-support legs constructed of open-ended pipe Mostbottom designs require “striker plates” under each roof support leg When the floating roof is landed, the pipe legs rest

on the striker plates supporting the weight of the roof Repeated, frequent contact between the striker plate and theopen end of the pipe leg removes any protective layer of rust scale that may have formed on the striker plate surface.When the roof is floated again, any water on the tank bottom causes corrosion at the location on the striker platewhere the coating and/or any protective rust scale has been damaged Experience has shown that frequent rooflandings over a long period of time causes corrosion severe and localized enough to corrode a hole through thestriker plate and the floor plate like a cookie cutter

5 Determination of the Need for Tank Bottom Lining

5.1 General

The bottom plates of aboveground storage tanks are susceptible to internal and external corrosion Storage tankbottoms are generally fabricated from carbon steel plate sections that are typically 0.25 in (6 mm) thick Annular floorplates of storage tanks frequently have thicker plate sections ranging from 0.25 in to 1.0 in (6 mm to 25 mm) Thebottom plate sections and the attachment fillet lap welds are intended to function as a membrane and prevent leaks.Uniform soil support beneath the bottom plate minimizes stress in the bottom plate

The need for an internal tank bottom lining in an aboveground storage tank is generally based on severalconsiderations:

a) corrosion prevention;

b) tank design;

c) tank history;

d) environmental considerations;

e) reduce time and effort for future tank cleaning;

f) federal, state, and local regulations;

g) product quality;

h) considerations under API Standard 653 with respect to next inspection interval

5.2 Linings for Corrosion Prevention

The proper selection, application, and maintenance of tank bottom linings can prevent internal corrosion of the steeltank bottom Unless means of corrosion prevention are used on the soil side, perforation of the tank bottom may stilloccur

The minimum thickness of the steel tank bottom should be determined according to API 653 An internal tank bottomlining may be deemed necessary if corrosion is expected to proceed so that the steel thickness may reach thisminimum thickness, generally 0.100 in (2.5 mm), prior to the next scheduled inspection

If the minimum bottom thicknesses at the end of the in-service period of operation are calculated to be less than theminimum bottom renewal thicknesses given in API 653, or less than the minimum bottom renewal thicknessesproviding acceptable risk as determined by an RBI assessment per API 653, the bottom shall be lined, repaired,replaced, or the interval to the next internal inspection shortened

When using API 653 to determine appropriate internal inspection intervals for aboveground storage tanks, theanticipated life of the lining as well as the corrosion rate anticipated in the event of premature lining failure should beconsidered.

5.3 Tank Corrosion History

The corrosion history of a particular tank should be considered when determining the need for an internal lining Thecorrosion history of tanks in similar service should also be considered The items to be considered are dictated byindividual circumstances, but some of the more important considerations are as follows

a) Where is the corrosion occurring (product side, soil side, or both)?

b) What is the internal and soil-side corrosion rate?

c) Have there been significant changes in the corrosion rate?

d) Is the corrosion uniform or localized?

e) Has corrosion caused perforation of the steel tank bottom?

f) What was the prior service of the tank and how corrosive was that product?

5.4 Tank Foundation

The foundation must be adequate to prevent excessive settlement of the tank If uniform foundation support is notprovided, flexing of the tank bottom can result as the tank is filled or emptied Flexing occurs on all steel floors;however, excessive flexing of the steel bottom may cause an internal bottom lining to crack

The tank pad material beneath the steel bottom has a significant effect on the potential for underside corrosion Ifthere is pad contamination (e.g rock, lumps of clay, welding electrodes, paper, plastic, wood, etc.) in contact with theunderside of the steel, differential aeration or other corrosion cells can form where the contaminates are in contactwith the tank bottom and severe corrosion may result (see API 651) The use of wood under a tank floor is notrecommended given that it promotes bacterial activity and will cause accelerated corrosion

6 Tank Bottom Lining Selection

6.1 General

Tank bottom linings can generally be divided into two classes: thin-films [with a dry film thickness less than 20 mils(500 µm)] and thick-films [with a dry film thickness of 20 mils (500 µm) or more] Linings may be applied to thebottoms of storage tanks when they are first constructed or they may be installed after some period of service.Generally, thin-film linings may be applied to new tanks and to bottoms of storage tanks that have experiencedminimal corrosion The advantages and disadvantages of thin and thick-film tank bottom lining systems are discussed

in this section

Most tank bottom lining materials are initially selected based on chemical resistance or compatibility with the storedproduct However, resistance to moisture permeation should also be a major consideration for long-term service sincemost storage tanks will typically have a layer of water on the floor All lining materials absorb moisture over time andthis absorption can ultimately result in its failure The moisture vapor transmission of various lining materials can becomparatively tested using ASTM E96, ASTM G9, or other equivalent test methods Because tank bottoms flexduring operation, a bend test on coating candidates should be performed to ASTM standards prior to coatingselection