1、StandardRecommended PracticeMaterials for the Handling and Storage of CommercialConcentrated (90 to 100%) Sulfuric Acid at AmbientTemperaturesThis NACE International standard represents a consensus of those individual members who havereviewed this document, its scope, and provisions. Its acceptance
2、does not in any respectpreclude anyone, whether he has adopted the standard or not, from manufacturing, marketing,purchasing, or using products, processes, or procedures not in conformance with this standard.Nothing contained in this NACE International standard is to be construed as granting any rig
3、ht, byimplication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, orproduct covered by Letters Patent, or as indemnifying or protecting anyone against liability forinfringement of Letters Patent. This standard represents minimum requirements and should in noway b
4、e interpreted as a restriction on the use of better procedures or materials. Neither is thisstandard intended to apply in all cases relating to the subject. Unpredictable circumstances maynegate the usefulness of this standard in specific instances. NACE International assumes noresponsibility for th
5、e interpretation or use of this standard by other parties and acceptsresponsibility for only those official NACE International interpretations issued by NACEInternational in accordance with its governing procedures and policies which preclude theissuance of interpretations by individual volunteers.U
6、sers of this NACE International standard are responsible for reviewing appropriate health, safety,environmental, and regulatory documents and for determining their applicability in relation to thisstandard prior to its use. This NACE International standard may not necessarily address allpotential he
7、alth and safety problems or environmental hazards associated with the use ofmaterials, equipment, and/or operations detailed or referred to within this standard. Users of thisNACE International standard are also responsible for establishing appropriate health, safety, andenvironmental protection pra
8、ctices, in consultation with appropriate regulatory authorities ifnecessary, to achieve compliance with any existing applicable regulatory requirements prior to theuse of this standard.CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may berevised or withdrawn at a
9、ny time without prior notice. NACE International requires that action betaken to reaffirm, revise, or withdraw this standard no later than five years from the date of initialpublication. The user is cautioned to obtain the latest edition. Purchasers of NACE Internationalstandards may receive current
10、 information on all standards and other NACE Internationalpublications by contacting the NACE International Membership Services Department, 1440 SouthCreek Drive, Houston, Texas 77084-4906 (telephone +1 281228-6200).Revised 2001-06-15Approved August 1991NACE International1440 South Creek DriveHousto
11、n, TX 77084-4906+1 281/228-6200ISBN 1-57590-126-92001, NACE InternationalNACE Standard RP0391-2001Item No. 21050RP0391-2001NACE International i_ForewordThis standard recommended practice provides information for use in the design and selection ofmaterials used in the handling and storage of commerci
12、al concentrated sulfuric acid (H2SO4)atambient temperatures. Currently there is no uniform, industry-wide standard for handling sulfuricacid. The primary purpose of this standard is to provide information allowing the reader to make amore informed decision regarding the design and selection of mater
13、ials. Only in sectionscontaining information about which there is general agreement among users are specificrecommendations made. This standard is intended to assist engineers and operations andmaintenance personnel in the chemical process industries (CPI) who are involved in the design,modification
14、, and maintenance of ambient-temperature, concentrated sulfuric acid systems andequipment.This standard was originally prepared in 1991 by NACE Task Group T-5A-18, a component of UnitCommittee T-5A on Corrosion in Chemical Processes. It was revised in 2001 by Task Group 216.This Task Group was compo
15、sed of industry representatives from firms producing and usingsulfuric acid. It is administered by Specific Technology Group (STG) 36 on ProcessIndustryChemicals, and is sponsored by STG 03 on Protective Coatings andLiningsImmersion/Buried. This standard is issued by NACE under the auspices of STG 3
16、6.In NACE standards, the terms shall, must, should, and may are used in accordance with thedefinitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shalland must are used to state mandatory requirements. Should is used to state something consideredgood and is rec
17、ommended but is not mandatory. May is used to state something consideredoptional._RP0391-2001ii NACE International_NACE InternationalStandardRecommended PracticeMaterials for the Handling and Storage of CommercialConcentrated (90 to 100%) Sulfuric Acid at AmbientTemperaturesContents1. General 12. Sp
18、ecific Materials . 13. Specific Equipment . 34. Safety Considerations. 6References 6Bibliography 6Appendix A: Listing of Alloys 7Appendix B: Sulfuric Adic Dilution System. 10TablesTable A1: Chemical Compositions. 7_RP0391-2001NACE International 1_Section 1: General1.1 This standard provides informat
19、ion about the designand selection of materials used in the handling and storageof commercial concentrated sulfuric acid at ambienttemperatures. The term ambient is intended to includetemperatures up to 50C (120F). This is the approximatemaximum temperature that arises from solar heating ofpiping or
20、vessels in a tropical climate.1.2 This standard does not consider sulfuric acid strengthsabove 100% or below 90% by weight.1.3 For completeness, this standard includes Appendix A,containing a listing of all alloys mentioned in this standard,and Appendix B, which gives guidance on applicablematerials
21、 for a sulfuric acid dilution system.1.4 Concentrated sulfuric acid is a colorless, odorless,syrupy liquid whose oily appearance suggested the nameoleum (Latin for oil) to early chemists.(1)Today, the termoleum is used only for sulfuric acid containing free sulfurtrioxide. The term sulfuric acid is
22、used to refer to acid thatdoes not contain free sulfur trioxide.1.5 The term concentrated sulfuric acid broadly refers tothe concentration range of 90 to 100% by weight.Commercial acid is usually stored at 93% concentrationbecause its minimum freezing point is 34C (30F). Sulfuricacid is commonly tra
23、nsported in the 98 to 99.5%concentration range. The latter limit is imposed by themuch greater corrosiveness of 100% sulfuric acid to carbonsteel and by its higher freezing point of about 7C (45F).1.6 Concentrated sulfuric acid is an oxidizing agent, andbecause of its affinity for water, it is also
24、a desiccant. Themajor problems in its handling and storage relate to itshygroscopic nature (absorbing atmospheric humidity), theexothermic reactivity with water on dilution, and velocityeffects that tend to accelerate corrosion of iron- and lead-based alloys._Section 2: Specific Materials2.1 Carbon
25、Steel2.1.1 Carbon steel is satisfactorily resistant toconcentrated sulfuric acid at ambient temperaturesunder static or low-velocity conditions (less than 0.9m/s 3 ft/s); for some restrictions, see Paragraphs2.1.4 and 3.3.6. The initially high corrosion rate isquickly reduced by the formation of an
26、insoluble sulfatefilm that is highly protective unless physically disturbed.However, even at nominal flow velocities within theprescribed limits, rapid, localized attack may occur.For example, short-radius elbows or excessive internalprotrusion of circumferential welds may causedownstream turbulence
27、 resulting in high corrosionrates.2.1.2 An important form of accelerated localized attackis hydrogen grooving on vertical or inclined wallsexposed to the liquid phase in piping or vessels.Hydrogen grooving is caused by evolution andmovement of hydrogen bubbles, resulting indeterioration of the prote
28、ctive film.2.1.3 Anodic protection is effective in minimizingcorrosion and preventing hydrogen grooving.2.1.4 In the 99.5 to 100% concentration range,increased corrosion rates may limit the fitness ofcarbon steel. The actual corrosion rate is stronglyaffected by temperature, acid concentration, ferr
29、ousand ferric ion concentration, flow conditions, andchloride contamination, because these parametersdetermine the dissolution rate and stability of theprotective iron-sulfate film.2.1.5 In all steel fabrication, weldments shall bethoroughly inspected to ensure that they do not containslag, porosity
30、, laps, or other welding defects that mayinitiate accelerated corrosion. Steel vessels and pipingmust also be free of mill scale, or serious local attackmay occur (see also Paragraph 3.1.7).2.1.6 Because of a lack of internal smoothnessresulting in localized turbulence, threaded or socket-welded pip
31、ing may cause accelerated corrosion. As analternative, butt-welded and flanged carbon steel pipinghave been used successfully (see also Paragraph3.1.6)._(1)Sulfuric acid was called oil of vitriol (from the Latin vitreum for glass) because of the glassy appearance of some metallic sulfates.RP0391-200
32、12 NACE International2.2 Cast Iron2.2.1 Gray cast iron and ductile cast iron are bothmore resistant to corrosion by concentrated sulfuricacid than is carbon steel. Velocities up to 1.5 m/s (4.9ft/s) can be tolerated. Frequently, velocities up to 2 m/s(7 ft/s) are accepted in large-diameter pipe(appr
33、oximately 350 mm 14 in. in diameter and larger),but accelerated corrosion may occur at joints andbends as a result of flow disturbance.2.2.2 Gray cast iron has lost favor in recent yearsbecause of its brittle nature. Catastrophic ruptureshave occurred in piping as well as pressure vessels.Ductile ca
34、st iron has been used successfully for thick-wall piping and is recommended over gray iron.Gaskets used with ductile iron piping should match thepipe bore to minimize acid turbulence.2.2.3 High-silicon cast irons (UNS(2)F47003 with14.5% Si) are resistant but are seldom used for simplehandling and st
35、orage because of their inherentbrittleness.2.3 Stainless Steel2.3.1 The conventional austenitic stainless steels ofthe Cr-Ni and Cr-Ni-Mo type are generally resistant toambient-temperature, concentrated acid because theyhave a naturally formed passive film. UNS S31600 issuitably resistant within the
36、 90 to 100% concentrationrange. UNS S30400 should only be used atconcentrations of 93% or greater. Conventionalaustenitic stainless steel grades find application inpiping in which moderately high velocity is a factor or inareas where iron contamination of the acid must beminimized. Although intergra
37、nular corrosion ofsensitized stainless steel is not a problem inconcentrated acid, the low-carbon grades (UNSS30403 and UNS S31603) are used for welded pipingsystems to prevent intergranular attack if dilution orcontamination can occur.2.3.2 The molybdenum-bearing grades (e.g., UNSS31600/S31603 or U
38、NS J92900/J92800) arerecommended for improved resistance to velocity-enhanced corrosion or impingement in valves in theentire concentration range.2.3.3 Duplex stainless steels have found successfulapplications in ambient-temperature concentrated acid,in the form of valves and pumps cast from copper-
39、bearing UNS J93370 and fabricated components fromwrought UNS S31803 material. These alloys aregenerally limited to acid strengths greater than or equalto 93%, but offer improved resistance to occasionaldilute acid formed during shutdowns when comparedwith conventional austenitic stainless steels (UN
40、SS31603 and UNS S30403).2.3.4 Any surface contamination by chlorides (e.g.,sea salt from transportation or storage under marineconditions) can cause rapid localized pitting. To acertain degree, molybdenum-bearing grades can copewith these conditions, but provisions for protection fromchloride contam
41、ination should be considered.2.3.5 Four to six percent silicon-containing stainlesssteels (UNS S30600, UNS S30601, and UNS S32615)perform very well in ambient-temperature, concentratedsulfuric acid, but are more typically used for high-temperature, turbulent applications found in sulfuricacid produc
42、tion plants.2.4 High-Nickel Stainless Steels and Nickel Alloys2.4.1 Nickel chromium-iron-copper-molybdenumalloys or their cast versions (see Appendix A) performbetter and are more resistant to concentrated acid than18Cr-10Ni-Mo stainless steel under the increasedvelocity conditions found in pumps an
43、d valves.2.4.2 Alloys of the nickel-chromium-molybdenum type,such as UNS N10276, UNS N06625, UNS N06022,UNS N06455, UNS N06985, UNS N06059, UNSN06200, and UNS N06686 or their cast versions, offerexcellent resistance to concentrated acid and areespecially useful for applications in which hightemperat
44、ures and significant acid strength variationsare possible.2.5 Other Alloys and Metals2.5.1 Nonferrous metals such as zinc, tin, copper, andnickel are not resistant to sulfuric acid and thereforehave no useful applications in its handling and storage.Aluminum grades UNS A91100, UNS A93003, andUNS A93
45、004 have been used successfully for handlingsulfuric acid in the concentration range of 98 to 100%,but are not generally recommended.2.5.2 Chemical lead is resistant to sulfuric acid but theprotective sulfate film is increasingly solubilized aboveabout 95% concentration and 25C (77F). The film iseas
46、ily damaged by velocity-accelerated corrosion evenat low velocities. It is very useful as a pan material tocatch dripping acid, which is diluted upon exposure tomoist air. However, because the acid always picks upand/or dissolves some lead, disposal of the acid is anenvironmental concern._(2)Metals
47、and Alloys in the Unified Numbering System (latest revision), a joint publication of the American Society for Testing and Materials(ASTM), 100 Barr Harbor Dr., West Conshohocken, PA 19428, and the Society of Automotive Engineers Inc. (SAE), 400 CommonwealthDrive, Warrendale, PA 15096.RP0391-2001NACE
48、 International 32.5.3 Of the reactive metals, titanium and zirconiummust not be exposed to concentrated acid. Tantalumis resistant to concentrations up to 97% acid and thusfinds some application, especially as an electroplatedcoating for orifice plates.2.5.4 Of the noble metals, gold and platinum areresistant to sulfuric acid but of very limited applicability.Gold is used to condense and cool reagent-g
