ASTM A380-2013.pdf | Stainless Steel | Corrosion

Please download to get full document.

View again

of 13
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Information Report
Category:

Documents

Published:

Views: 291 | Pages: 13

Extension: PDF | Download: 7

Share
Related documents
Description
Designation: A380/A380M − 13 Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems1 This standard is issued under the fixed designation A380/A380M; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates th
Transcript
  Designation: A380/A380M  −  13 Standard Practice for Cleaning, Descaling, and Passivation of Stainless SteelParts, Equipment, and Systems 1 This standard is issued under the fixed designation A380/A380M; the number immediately following the designation indicates the yearof srcinal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval.A superscript epsilon ( ´ ) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. 1. Scope* 1.1 This practice covers recommendations and precautionsfor cleaning, descaling, and passivating of new stainless steelparts, assemblies, equipment, and installed systems. Theserecommendations are presented as procedures for guidancewhen it is recognized that for a particular service it is desiredto remove surface contaminants that may impair the normalcorrosion resistance, or result in the later contamination of theparticular stainless steel grade, or cause product contamination.The selection of procedures from this practice to be applied tothe parts may be specified upon agreement between thesupplier and the purchaser. For certain exceptionalapplications, additional requirements which are not covered bythis practice may be specified upon agreement between thesupplier and the purchaser. Although they apply primarily tomaterials in the composition ranges of the austenitic, ferritic,and martensitic stainless steels, the practices described mayalso be useful for cleaning other metals if due consideration isgiven to corrosion and possible metallurgical effects.1.1.1 The term passivation is commonly applied to severaldistinctly different operations or processes relating to stainlesssteels. In order to avoid ambiguity in the setting of requirements, it may be necessary for the purchaser to defineprecisely the intended meaning of passivation. Some of thevarious meanings associated with the term passivation that arein common usage include the following:1.1.1.1 Passivation is the process by which a stainless steelwill spontaneously form a chemically inactive surface whenexposed to air or other oxygen-containing environments. It wasat one time considered that an oxidizing treatment was neces-sary to establish this passive film, but it is now accepted thatthis film will form spontaneously in an oxygen-containingenvironment providing that the surface has been thoroughlycleaned or descaled.1.1.1.2 Passivation is removal of exogenous iron or ironcompounds from the surface of a stainless steel by means of achemical dissolution, most typically by a treatment with anacid solution that will remove the surface contamination butwill not significantly affect the stainless steel itself. Thisprocess is described in a general way in 6.2.11 and definedprecisely in 6.4 with further reference to the requirements of Annex A2 and Part II of the table on acid cleaning of steel.Unless otherwise specified, it is this definition of passivationthat is taken as the meaning of a specified requirement forpassivation.1.1.1.3 Passivation is the chemical treatment of a stainlesssteel with a mild oxidant, such as a nitric acid solution, for thepurpose of enhancing the spontaneous formation of the protec-tive passive film. Such chemical treatment is generally notnecessary for the formation of the passive film.1.1.1.4 Passivation does not indicate the separate process of descaling as described in Section 5, although descaling may benecessary before passivation can be effective.1.2 This practice does not cover decontamination or clean-ing of equipment or systems that have been in service, nor doesit cover descaling and cleaning of materials at the mill. On theother hand, some of the practices may be applicable for thesepurposes. While the practice provides recommendations andinformation concerning the use of acids and other cleaning anddescaling agents, it cannot encompass detailed cleaning proce-dures for specific types of equipment or installations. Ittherefore in no way precludes the necessity for careful planningand judgment in the selection and implementation of suchprocedures.1.3 These practices may be applied when free iron, oxidescale, rust, grease, oil, carbonaceous or other residual chemicalfilms, soil, particles, metal chips, dirt, or other nonvolatiledeposits might adversely affect the metallurgical or sanitarycondition or stability of a surface, the mechanical operation of a part, component, or system, or contaminate a process fluid.The degree of cleanness required on a surface depends on theapplication. In some cases, no more than degreasing or removalof gross contamination is necessary. Others, such as food-handling, pharmaceutical, aerospace, and certain nuclearapplications, may require extremely high levels of cleanness, 1 This practice is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.14 on Methods of Corrosion Testing.Current edition approved Feb. 15, 2013. Published April 2013. Originallyapproved in 1954. Last previous edition approved in 2006 as A380 – 06. DOI:10.1520/A0380_A0380M-13 *A Summary of Changes section appears at the end of this standard Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States 1   Copyright by ASTM Int'l (all rights reserved); Fri Oct 3 19:28:48 EDT 2014Downloaded/printed byPontificia Universidad Catolica del Peru pursuant to License Agreement. No further reproductions authorized.  including removal of all detectable residual chemical films andcontaminants that are invisible to ordinary inspection methods. N OTE  1—The term “iron,” when hereinafter referred to as a surfacecontaminant, shall denote free iron. 1.4 Attainment of surfaces that are free of iron, metallicdeposits, and other contamination depends on a combination of proper design, fabrication methods, cleaning and descaling,and protection to prevent recontamination of cleaned surfaces.Meaningful tests to establish the degree of cleanness of asurface are few, and those are often difficult to administer andto evaluate objectively. Visual inspection is suitable for thedetection of gross contamination, scale, rust, and particulates,but may not reveal the presence of thin films of oil or residualchemical films. In addition, visual inspection of internalsurfaces is often impossible because of the configuration of theitem. Methods are described for the detection of free iron andtransparent chemical and oily deposits.1.5 This practice provides definitions and describes prac-tices for cleaning, descaling, and passivation of stainless steelparts. Tests with acceptance criteria to demonstrate that thepassivation procedures have been successful are listed in 7.2.5and 7.3.4 and can also be found in Specification A967. 1.6 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.7  This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.  (For more specificsafety precautions see 7.2.5.3, 7.3.4, Section 8, A1.7, and A2.11.) 2. Referenced Documents 2.1  ASTM Standards: 2 A967 Specification for Chemical Passivation Treatments forStainless Steel PartsF21 Test Method for Hydrophobic Surface Films by theAtomizer TestF22 Test Method for Hydrophobic Surface Films by theWater-Break Test2.2  Federal Standard: 3 Fed. Std. No. 209e for Clean Room and Work StationRequiring Controlled Environments 3. Design 3.1 Consideration should be given in the design of parts,equipment, and systems that will require cleaning to minimizethe presence of crevices, pockets, blind holes, undrainablecavities, and other areas in which dirt, cleaning solutions, orsludge might lodge or become trapped, and to provide foreffective circulation and removal of cleaning solutions. Inequipment and systems that will be cleaned in place or thatcannot be immersed in the cleaning solution, it is advisable toslope lines for drainage: to provide vents at high points anddrains at low points of the item or system; to arrange forremoval or isolation of parts that might be damaged by thecleaning solution or fumes from the cleaning solutions; toprovide means for attaching temporary fill and circulationlines; and to provide for inspection of cleaned surfaces.3.2 In a complex piping system it may be difficult todetermine how effective a cleaning operation has been. Onemethod of designing inspectability into the system is to providea short flanged length of pipe (that is, a spool piece) at alocation where the cleaning is likely to be least effective; thespool piece can then be removed for inspection upon comple-tion of cleaning. 4. Precleaning 4.1 Precleaning is the removal of grease, oil, paint, soil, grit,and other gross contamination preparatory to a fabricationprocess or final cleaning. Precleaning is not as critical and isgenerally not as thorough as subsequent cleaning operations.Materials should be precleaned before hot-forming, annealing,or other high-temperature operation, before any descalingoperation, and before any finish-cleaning operation where theparts will be immersed or where the cleaning solutions will bereused. Items that are subject to several redraws or a series of hot-forming operations, with intermediate anneals, must becleaned after each forming operation, prior to annealing.Precleaning may be accomplished by vapor degreasing; im-mersion in, spraying, or swabbing with alkaline or emulsioncleaners, steam, or high-pressure water-jet (see 6.2). 5. Descaling 5.1  General—  Descaling is the removal of heavy, tightlyadherent oxide films resulting from hot-forming, heat-treatment, welding, and other high-temperature operations.Because mill products are usually supplied in the descaledcondition, descaling (except removal of localized scale result-ing from welding) is generally not necessary during fabricationof equipment or erection of systems (see 6.3). Whennecessary, scale may be removed by one of the chemicalmethods listed below, by mechanical methods (for example,abrasive blasting, sanding, grinding, power brushing), or by acombination of these.5.2  Chemical Descaling (Pickling)—  Chemical descalingagents include aqueous solutions of sulfuric, nitric, and hydro-fluoric acid as described in Annex A1, Table A1.1, molten alkali or salt baths, and various proprietary formulations.5.2.1  Acid Pickling—  Nitric-hydrofluoric acid solution ismost widely used by fabricators of stainless steel equipmentand removes both metallic contamination, and welding andheat-treating scales. Its use should be carefully controlled andis not recommended for descaling sensitized austenitic stain-less steels or hardened martensitic stainless steels or where it 2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at service@astm.org. For  Annual Book of ASTM Standards  volume information, refer to the standard’s Document Summary page onthe ASTM website. 3 Available from Standardization Documents Order Desk, Bldg 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS. A380/A380M − 13 2   Copyright by ASTM Int'l (all rights reserved); Fri Oct 3 19:28:48 EDT 2014Downloaded/printed byPontificia Universidad Catolica del Peru pursuant to License Agreement. No further reproductions authorized.  can come into contact with carbon steel parts, assemblies,equipment, and systems. See also A1.3. Solutions of nitric acid alone are usually not effective for removing heavy oxide scale.5.2.2 Surfaces to be descaled are usually precleaned prior tochemical treatment. When size and shape of product permit,total immersion in the pickling solution is preferred. Whereimmersion is impractical, descaling may be accomplished by( 1 ) wetting the surfaces by swabbing or spraying; or ( 2 ) bypartially filling the item with pickling solution and rotating orrocking to slosh the solution so that all surfaces receive therequired chemical treatment. The surface should be kept incontact with agitated solution for about 15 to 30 min or untilinspection shows that complete scale removal has been accom-plished. Without agitation, additional exposure time may berequired. If rocking or rotation are impracticable, picklingsolution may be circulated through the item or system untilinspection shows that descaling has been accomplished.5.2.3 Over-pickling must be avoided. Uniform removal of scale with acid pickling depends on the acid used, acidconcentration, solution temperature, and contact time (seeAnnex A1). Continuous exposure to pickling solutions formore than 30 min is not recommended. The item should bedrained and rinsed after 30 min and examined to check theeffectiveness of the treatment. Additional treatment may berequired. Most pickling solutions will loosen weld and heat-treating scale but may not remove them completely. Intermit-tent scrubbing with a stainless steel brush or fiber-bristle brush,in conjunction with pickling or the initial rinse, may facilitatethe removal of scale particles and products of chemicalreaction (that is, pickling  smut  ).5.2.4 After chemical descaling, surfaces must be thoroughlyrinsed to remove residual chemicals; a neutralization step issometimes necessary before final rinsing. To minimizestaining, surfaces must not be permitted to dry betweensuccessive steps of the acid descaling and rinsing procedure,and thorough drying should follow the final water rinse.Chemical descaling methods, factors in their selection, andprecautions in their use are described in the  Metals Handbook  . 4 When chemical descaling is necessary, it should be done whilethe part is in its simplest possible geometry, before subsequentfabrication or installation steps create internal crevices orundrainable spaces that may trap descaling agents, sludge,particles, or contaminated rinse water that might either result ineventual corrosion or adversely affect operation of the itemafter it is placed in service.5.3  Mechanical Descaling—  Mechanical descaling methodsinclude abrasive blasting, power brushing, sanding, grinding,and chipping. Procedural requirements and precautions forsome of these methods are given in the  Metals Handbook  . 4 Mechanical descaling methods have the advantage that they donot produce such physical or chemical conditions as inter-granular attack, pitting, hydrogen embrittlement, cracks, orsmut deposits. For some materials, in particular the austeniticstainless steels when in the sensitized condition and themartensitic stainless steels when in the hardened condition,mechanical descaling may be the only suitable method. Grind-ing is usually the most effective means of removing localizedscale such as that which results from welding. Disadvantagesof mechanical descaling are cost, as compared to chemicaldescaling, and the fact that surface defects (for example, laps,pits, slivers) may be obscured, making them difficult to detect.5.3.1 Surfaces to be descaled may have to be precleaned.Particular care must be taken to avoid damage by mechanicalmethods when descaling thin sections, polished surfaces, andclose-tolerance parts. After mechanical descaling, surfacesshould be cleaned by scrubbing with hot water and fiberbrushes, followed by rinsing with clean, hot water.5.3.2 Grinding wheels and sanding materials should notcontain iron, iron oxide, zinc, or other undersirable materialsthat may cause contamination of the metal surface. Grindingwheels, sanding materials, and wire brushes previously used onother metals should not be used on stainless steel. Wire brushesshould be of a stainless steel which is equal in corrosionresistance to the material being worked on.5.3.3 Clean, previously unused abrasives, such as glassbeads or iron-free silica or alumina sand, are recommended forabrasive blasting. Steel shot or grit is generally not recom-mended because of the possibility of embedding iron particles.The use of stainless steel shot or grit reduces the danger of rusting and iron contamination, but cannot completely elimi-nate the possibility of embedding residues of iron-oxide scale.5.3.4 If a totally iron and scale free surface is required, mostabrasive blasting may be followed by a brief acid dip (seeAnnex A2). 6. Cleaning 6.1  General—  Cleaning includes all operations necessary forthe removal of surface contaminants from metals to ensure ( 1 )maximum corrosion resistance of the metal; ( 2 ) prevention of product contamination; and ( 3 ) achievement of desired appear-ance. Cleanness is a perishable condition. Careful planning isnecessary to achieve and maintain clean surfaces, especiallywhere a high degree of cleanness is required. Selection of cleaning processes is influenced mainly by the type of con-taminant to be removed, the required degree of cleanness, andcost. If careful control of fabrication processes, sequencing of cleaning and fabrication operations, and measures to preventrecontamination of cleaned surfaces are exercised, very littlespecial cleaning of the finished item or system may benecessary to attain the desired level of cleanness. If there is aquestion concerning the effectiveness of cleaning agents orprocedures, or the possible adverse effects of some cleaningagents or procedures on the materials to be cleaned, trial runs,using test specimens and sensitive inspection techniques maybe desirable. Descriptions, processes, and precautions to beobserved in cleaning are given in the  Metals Handbook  . 4 Proprietary cleaners may contain harmful ingredients, such aschlorides or sulfur compounds, which could adversely affectthe performance of a part, equipment, or system under serviceconditions. It is recommended that the manufacturer of thecleaner be consulted if there is reason for concern. N OTE  2—Instances are known where stainless steel vessels have stresscracked before start-up due to steaming out or boiling out with achloride-containing detergent. 4 “Surface Cleaning, Finishing, and Coating,”  Metals Handbook,  Am. Soc.Metals, 9th ed., Vol 5, 1982. A380/A380M − 13 3   Copyright by ASTM Int'l (all rights reserved); Fri Oct 3 19:28:48 EDT 2014Downloaded/printed byPontificia Universidad Catolica del Peru pursuant to License Agreement. No further reproductions authorized.  6.2  Cleaning Methods—  Degreasing and general cleaningmay be accomplished by immersion in, swabbing with, orspraying with alkaline, emulsion, solvent, or detergent cleanersor a combination of these; by vapor degreasing; by ultrasonicsusing various cleaners; by steam, with or without a cleaner; orby high-pressure water-jetting. The cleaning method availableat any given time during the fabrication or installation of acomponent or system is a function of the geometric complexityof the item, the type of contamination present, the degree of cleanliness required, and cost. Methods commonly used forremoving deposited contaminants (as opposed to scale) aredescribed briefly below and in greater detail (including factorsto be considered in their selection and use) in the  Metals Handbook  4 and the  SSPC Steel Structures Painting Hand-book. 5 The safety precautions of  8.6 must be observed in theuse of these methods. Particular care must be exercised whencleaning closed systems and items with crevices or internalvoids to prevent retention of cleaning solutions and residues.6.2.1  Alkaline Cleaning  is used for the removal of oily,semisolid, and solid contaminants from metals. To a greatextent the solutions used depend on their detergent qualities forcleaning action and effectiveness.Agitation and temperature of the solution are important.6.2.2  Emulsion Cleaning  is a process for removing oilydeposits and other common contaminants from metals by theuse of common organic solvents dispersed in an aqueoussolution with the aid of a soap or other emulsifying agent (anemulsifying agent is one which increases the stability of adispersion of one liquid in another). It is effective for removinga wide variety of contaminants including pigmented andunpigmented drawing compounds and lubricants, cuttingfluids, and residues resulting from liquid penetrant inspection.Emulsion cleaning is used when rapid, superficial cleaning isrequired and when a light residual film of oil is not objection-able.6.2.3  Solvent Cleaning  is a process for removing contami-nants from metal surfaces by immersion or by spraying orswabbing with common organic solvents such as the aliphaticpetroleums, chlorinated hydrocarbons, or blends of these twoclasses of solvents. Cleaning is usually performed at or slightlyabove room temperature. Except for parts with extremelyheavy contamination or with hard-to-reach areas, or both, goodagitation will usually eliminate the need for prolonged soaking.Virtually all metal can be cleaned with the commonly usedsolvents unless the solvent has become contaminated with acid,alkali, oil, or other foreign material. Chlorinated solvents arenot recommended for degreasing of closed systems or itemswith crevices or internal voids.6.2.4  Vapor Degreasing  is a generic term applied to acleaning process that employs hot vapors of a volatile chlori-nated solvent to remove contaminants, and is particularlyeffective against oils, waxes, and greases. The cleanness andchemical stability of the degreasing solvent are critical factorsin the efficiency of the vapor and possible chemical attack of the metal. Water in the degreasing tank or on the item beingcleaned may react with the solvent to form hydrochloric acid,which may be harmful to the metal. No water should be presentin the degreasing tank or on the item being cleaned. Acids,oxidizing agents, and cyanides must be prevented from con-taminating the solvent. Materials such as silicones causefoaming at the liquid-vapor interface and may result inrecontamination of the workpiece as it is removed from thedegreaser. Vapor degreasing with chlorinated solvents is notrecommended for closed systems or items with internal voidsor crevices.6.2.5  Ultrasonic Cleaning  is often used in conjunction withcertain solvent and detergent cleaners to loosen and removecontaminants from deep recesses and other difficult to reachareas, particularly in small work-pieces. Cavitation in theliquid produced by the high frequency sound causes microagitation of the solvent in even tiny recesses of the workpiece,making the method especially desirable for cleaning parts orassemblies having an intricate configuration. For extremelyhigh levels of surface cleanness, high-purity solvents (1 ppmtotal nonvolatile residue) are required.6.2.6  Synthetic Detergents  are extensively used as surface-active agents because they are freer rinsing than soaps, aid insoils dispersion, and prevent recontamination. They are effec-tive for softening hard water and in lowering the surface andinterfacial tensions of the solutions. Synthetic detergents, inparticular, should be checked for the presence of harmfulingredients as noted in 6.1.6.2.7  Chelate Cleaning—  Chelates are chemicals that formsoluble, complex molecules with certain metal ions, inactivat-ing the ions in solution so they cannot normally react withanother element or ions to produce precipitates or scale. Theyenhance the solubility of scales and certain other contaminants,do not precipitate different scales when the cleaning solutionbecomes spent, and can be used on some scales and contami-nants that even mineral acids will not attack. When properlyused (chelating agents must be continuously circulated andmust be maintained within carefully controlled temperaturelimits), intergranular attack, pitting, and other harmful effectsare minimal. Chelating agents are particularly useful forcleaning installed equipment and systems.6.2.8  Mechanical Cleaning  (also see 5.3)  —  Abrasiveblasting, vapor blasting using a fine abrasive suspended inwater, grinding, or wire brushing are often desirable forremoving surface contaminants and rust. Cleanliness of abra-sives and cleaning equipment is extremely important to preventrecontamination of the surfaces being cleaned. Although sur-faces may appear visually clean following such procedures,residual films which could prevent the formation of an opti-mum passive condition may still be present. Subsequenttreatment such as additional iron-free abrasive cleaningmethods, acid cleaning, passivation, or combinations of theseis, therefore, required for stainless steel parts, equipment, andsystems to be used where corrosion resistance is a prime factorto satisfy performance and service requirements, or whereproduct contamination must be avoided.6.2.9  Steam Cleaning  is used mostly for cleaning bulkyobjects that are too large for soak tanks or spray-washing 5 Good Painting Practices,  Steel Structures Painting Council, Vol 1, 1982,Chapters 2.0–2.9, 3.1–3.2. A380/A380M − 13 4   Copyright by ASTM Int'l (all rights reserved); Fri Oct 3 19:28:48 EDT 2014Downloaded/printed byPontificia Universidad Catolica del Peru pursuant to License Agreement. No further reproductions authorized.
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks