1、Designation: A 380 06Standard Practice forCleaning, Descaling, and Passivation of Stainless SteelParts, Equipment, and Systems1This standard is issued under the fixed designation A 380; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisio
2、n, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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
3、 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 contamin
4、ants that may impair the normalcorrosion resistance, or result in the later contamination of theparticular stainless steel grade, or cause product contamination.For certain exceptional applications, additional requirementswhich are not covered by this practice may be specified uponagreement between
5、the manufacturer and the purchaser. Al-though they apply primarily to materials in the compositionranges of the austenitic, ferritic, and martensitic stainlesssteels, the practices described may also be useful for cleaningother metals if due consideration is given to corrosion andpossible metallurgi
6、cal 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 require-ments, it may be necessary for the purchaser to define preciselythe intended meaning of passivation. So
7、me of the variousmeanings associated with the term passivation that are incommon 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 tim
8、e 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 o
9、r 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 stainlees steel itself. Thisprocess is described in a general way in 6.2.11 and
10、definedprecisely in 6.4 with further reference to the requirements ofAnnex 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
11、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
12、separate process ofdescaling 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
13、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 insta
14、llations. 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,
15、 dirt, or other nonvolatiledeposits might adversely affect the metallurgical or sanitarycondition or stability of a surface, the mechanical operation ofa part, component, or system, or contaminate a process fluid.The degree of cleanness required on a surface depends on theapplication. In some cases,
16、 no more than degreasing or removal1This 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 May 1, 2006. Published May 2006. Originallyapp
17、roved in 1954. Last previous edition approved in 2005 as A 380 99 (2005).1*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.of gross contamination is necessary. Others, s
18、uch as food-handling, pharmaceutical, aerospace, and certain nuclear ap-plications, may require extremely high levels of cleanness,including removal of all detectable residual chemical films andcontaminants that are invisible to ordinary inspection methods.NOTE 1The term “iron,” when hereinafter ref
19、erred 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 ofproper design, fabrication methods, cleaning and descaling,and protection to prevent recontamination of cleaned surfaces.Mea
20、ningful 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
21、 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 goodpratices fo
22、r cleaning, descaling, and passivation of stainlesssteel parts, but does not provide tests with acceptance criteriato demonstrate that the passivation procedures have beensuccessful. For such tests, it is appropriate to specify one of thepractices listed in Specification A 967.1.6 This standard does
23、 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
24、 see 7.2.5.3, 7.3.4, Section 8, A1.7, andA2.11.)2. Referenced Documents2.1 ASTM Standards:2A 967 Specification for Chemical Passivation Treatmentsfor Stainless Steel PartsF21 Test Method for Hydrophobic Surface Films by theAtomizer TestF22 Test Method for Hydrophobic Surface Films by theWater-Break
25、Test2.2 Federal Standard:3Fed. Std. No. 209e for Clean Room and Work StationRequiring Controlled Environments3. Design3.1 Consideration should be given in the design of parts,equipment, and systems that will require cleaning to minimizethe presence of crevices, pockets, blind holes, undrainablecavit
26、ies, 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
27、 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 t
28、o 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 c
29、leaning is likely to be least effective; thespool piece can then be removed for inspection upon comple-tion of cleaning.4. Precleaning4.1 Precleaning is the removal of grease, oil, paint, soil, grit,and other gross contamination preparatory to a fabricationprocess or final cleaning. Precleaning is n
30、ot 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 clea
31、ning solutions will bereused. Items that are subject to several redraws or a series ofhot-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 alka
32、line or emulsioncleaners, steam, or high-pressure water-jet (see 6.2).5. Descaling5.1 GeneralDescaling 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 des
33、caledcondition, descaling (except removal of localized scale result-ing from welding) is generally not necessary during fabricationof equipment or erection of systems (see 6.3). When neces-sary, scale may be removed by one of the chemical methodslisted below, by mechanical methods (for example, abra
34、siveblasting, sanding, grinding, power brushing), or by a combi-nation of these.5.2 Chemical Descaling (Pickling)Chemical descalingagents include aqueous solutions of sulfuric, nitric, and hydrof-luoric acid as described inAnnexA1, TableA1.1, molten alkalior salt baths, and various proprietary formu
35、lations.5.2.1 Acid PicklingNitric-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 st
36、ain-less steels or hardened martensitic stainless steels or where itcan come into contact with carbon steel parts, assemblies,equipment, and systems. See also A1.3. Solutions of nitric acidalone are usually not effective for removing heavy oxide scale.2For referenced ASTM standards, visit the ASTM w
37、ebsite, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from Standardization Documents Order Desk, Bldg 4 Section D, 700Robbins Ave., Philadelphia, PA 191
38、11-5094, Attn: NPODS.A3800625.2.2 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 swabbin
39、g 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
40、 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. U
41、niform removal ofscale 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 theef
42、fectiveness 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 f
43、acilitatethe 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 minimize stain-ing, surfaces must not
44、 be permitted to dry between successivesteps of the acid descaling and rinsing procedure, and thoroughdrying should follow the final water rinse. Chemical descalingmethods, factors in their selection, and precautions in their useare described in the Metals Handbook.4When chemicaldescaling is necessa
45、ry, it should be done while the part is in itssimplest possible geometry, before subsequent fabrication orinstallation steps create internal crevices or undrainable spacesthat may trap descaling agents, sludge, particles, or contami-nated rinse water that might either result in eventual corrosionor
46、adversely affect operation of the item after it is placed inservice.5.3 Mechanical DescalingMechanical descaling methodsinclude abrasive blasting, power brushing, sanding, grinding,and chipping. Procedural requirements and precautions forsome of these methods are given in the Metals Handbook.4Mechan
47、ical 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 themartensi
48、tic 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,
49、 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 ca
