1、 Standard Practice Preparation, Installation, Analysis, and Interpretation of Corrosion Coupons in Oilfield Operations This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respec
2、t preclude anyone, whether he or she 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 right, by impli
3、cation or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no way be interp
4、reted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility for the int
5、erpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Us
6、ers of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address all potential
7、health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental protectio
8、n practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withd
9、rawn at any time in accordance with NACE technical committee procedures. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication and subsequently from the date of each reaffirmation or revision. The
10、 user is cautioned to obtain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Dr., Houston, Texas 77084-4906 (teleph
11、one +1 281-228-6200). Reaffirmed 2012-09-05 Reaffirmed 2005-04-07 Revised 1999-06-25 Revised 1991 Revised 1987 Approved 1975 NACE International 1440 South Creek Dr. Houston, Texas 77084-4906 +1-281-228-6200 ISBN 1-57590-086-6 2013, NACE International SP0775-2013 (formerly RP0775) Item No. 21017 SP07
12、75-2013 NACE International i _ Foreword This standard practice was prepared to encourage the use of uniform and industry-proven methods to monitor mass-loss and pitting corrosion in oilfield operations. This standard outlines procedures for preparing, installing, and analyzing metallic corrosion cou
13、pons. Factors considered in the interpretation of results obtained from these corrosion coupons are also included for the use of oil and service industry personnel. This standard was originally prepared in 1975 by NACE Task Group T-1C-6, a component of Unit Committee T-1C, “Detection of Corrosion in
14、 Oil Field Equipment,” to provide procedures for the preparation, installation, and analysis of corrosion coupons. It was revised by Task Group T-1C-11 in 1986 and by T-1C-23 in 1991. T-1C was combined with Unit Committee T-1D, “Corrosion Monitoring and Control of Corrosion Environments in Petroleum
15、 Production Operations,” and this standard was revised by Task Group T-1D-54 in 1999. It was reaffirmed in 2005 and in 2012 by Specific Technology Group (STG) 31, “Oil and Gas ProductionCorrosion and Scale Inhibition.” This standard is issued by NACE International under the auspices of STG 31. In NA
16、CE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms shall and must are used to state a requirement, and are considered mandatory. The term should is used to state something good and is recomm
17、ended, but is not considered mandatory. The term may is used to state something considered optional. _ SP0775-2013 ii NACE International _ Standard Practice Preparation, Installation, Analysis, and Interpretation of Corrosion Coupons in Oilfield Operations Contents 1. General 1 2. Processing of Corr
18、osion Coupons .1 3. Installation of Corrosion Coupons 7 4. Recording Data on Corrosion Coupon Report . 16 5. Interpretation of Corrosion Coupon Data . 16 References 17 Appendix A: Typical Corrosion Coupon Report (Nonmandatory) 19 FIGURES Figure 1: Circular (washer-type) coupon and typical mounting i
19、n a ring joint flange. .8 Figure 2: Drill pipe corrosion ring coupon .9 Figure 3: Flat coupon holder using a 60 mm nominal OD (2 in NPT) threaded pipe plug .9 Figure 4: Round (rod-type) coupon holder using a 60 mm nominal OD (2 in NPT) threaded pipe plug and special insulating disk that can accommod
20、ate eight round (rod-type) coupons 11 Figure 5: Tool for installing and removing coupons in systems under pressure. . 12 Figure 6: Extractor tool for inserting and removing coupons in systems under pressure. . 12 Figure 7: Wire-line-operated tubing stop adapted as downhole coupon holder. . 14 Figure
21、 8: Choice of location for coupon installation and interpretation of coupon corrosion rate measurements . 15 TABLES Table 1: Density of Metals .5 Table 2: Qualitative Categorization of Carbon Steel Corrosion Rates for Oil Production Systems 17 _ SP0775-2013 NACE International 1 _ Section 1: General
22、1.1 This standard is presented for the use of corrosion coupons in oilfield drilling, production, and transportation operations. Oilfield operations include oil-, water-, and gas-handling systems, and drilling fluids. (When used in this standard, system denotes a functional unit such as a producing
23、well; flowline and tank battery; water, oil, or gas collection facility; water or gas injection facility; or a gas dehydration or sweetening unit.) Corrosion coupon testing consists of the exposure of a small specimen of metal (the coupon) to an environment of interest for a period of time to determ
24、ine the reaction of the metal to the environment. Corrosion coupons are used to evaluate corrosiveness of various systems, to monitor the effectiveness of corrosion-mitigation programs, and to evaluate the suitability of different metals for specific systems and environments. The coupons may be inst
25、alled in the system itself or in a special test loop or apparatus. Corrosion rates shown by coupons and most other corrosion-monitoring devices seldom duplicate the actual rate of corrosion on the system piping and vessels. Accurate system corrosion rates can be determined by nondestructive measurem
26、ent methods or failure frequency curves. Data furnished by corrosion coupons and other types of monitors must be related to system requirements. High corrosion rates on coupons may be used to verify the need for corrective action. If a corrosion-mitigation program is initiated and subsequent coupon
27、data indicate that corrosion has been reduced, the information can be used to approximate the effectiveness of the mitigation program. This standard does not contain information on monitoring for intergranular corrosion, stress corrosion cracking (SCC), or sulfide stress cracking (SSC). The latter a
28、spects are discussed elsewhere.1,2 1.2 This standard describes preparation and handling techniques for metal coupons prior to and following exposure. Corrosion rate calculations and a typical form for recording data are also included. 1.3 Coupon size, metal composition, surface condition, and coupon
29、 holders may vary according to the test system design or the users requirements. Coupons are often installed in pairs for simultaneous removal and average mass-loss determination. Coupons may be used alone but they should be used in conjunction with other monitoring methods such as test nipples, hyd
30、rogen probes, galvanic probes, polarization instruments, resistance-type corrosion monitors, chemical analysis of process streams and nondestructive metal thickness measurements, caliper surveys, and corrosion failure records. 1.4 Corrosion coupons used as recommended in this standard measure the to
31、tal metal loss during the exposure period. They show corrosion that has already occurred. A single coupon cannot be used to determine whether the rate of metal loss was uniform or varying during the exposure period. Information on the change in corrosion rate can be obtained by installing several co
32、upons at one time and removing and evaluating individual coupons at specific short-term intervals. Other monitoring methods mentioned in Paragraph 1.3 can be used to provide more accurate information on short-term rates of corrosion. Data provided by corrosion coupons can provide excellent backup fo
33、r “event-indicating” corrosion-monitoring instruments. 1.5 In addition to mass loss, important factors to consider in the analysis and interpretation of coupon data include location, time onstream, measured pit depth, surface profile (blistering, erosion), corrosion product and/or scale composition,
34、 and operating factors (e.g., downtime, system flow velocities, upsets, or inhibition). 1.6 Coupon corrosion rates in one system should not be compared directly with those in other unrelated systems. However, corrosion rates in similar systems (e.g., two systems handling identical environments) ofte
35、n correlate. Additional information can be obtained within a system by varying one exposure parameter at a time (e.g., location or duration of exposure). For example, corrosion rates can be affected by changes in fluid velocity within a system. Corrosion rates can vary dramatically upstream and down
36、stream from the point of entry of a corrodent, such as oxygen. _ Section 2: Processing of Corrosion Coupons 2.1 Coupon Preparation. The following procedure should be used to prepare coupons for corrosion testing. Coupons should be new; do not reuse coupons after exposure and analysis. 2.1.1 Choose a
37、 method of coupon preparation that does not alter the metallurgical properties of the metal. Grinding operations must be controlled to avoid high surface temperatures that could change the microstructure of the coupon. 2.1.2 Etch or stamp a permanent serial number on the coupon. It is possible for a
38、 coupon or holder to undergo SCC if the conditions in Paragraphs 2.1.2.1 and 2.1.2.2 are met: 2.1.2.1 Exposure to an environment capable of cracking the alloy used for the coupon or holder. SP0775-2013 2 NACE International 2.1.2.2 Stress sufficiently high to cause cracking. Such stress can result fr
39、om a combination of residual stress (such as introduced by stamping) and imposed stress. 2.1.2.3 Instances of SCC of carbon steel coupons under oilfield conditions have rarely been reported. Nevertheless, broken pieces of coupons or holders can lodge downstream in valves and interfere with their nor
40、mal operation. 2.1.3 Machine or polish the edges of the coupon to remove cold-worked metal if the cold-worked edges adversely affect the data. Coupons formed by stamping are less expensive than machined coupons. Stamped coupons are satisfactory without additional machining for most oilfield monitori
41、ng. 2.1.4 Ideally, match the surface finish of the coupons with the finish of the metal being investigated, i.e., the pipe or vessel wall. Because this is seldom practical, other surface finishes are applied. No specific surface finish is absolutely essential but uniformity is very important when da
42、ta from different sets of coupons are being compared. Coupons may be prepared by grinding smooth with 120 grit paper, by tumbling with loose grit, or blasting with abrasive blasting material. A consistent finish may be obtained by blasting with glass beads, but glass beads may not remove mill scale
43、or rust. All abrasives should be free of metallic particles. 2.1.5 After the coupons have been cleaned, handle them by suitable means to prevent contamination of the surface with oils, body salts, and other foreign materials. Clean, lint-free cotton gloves or cloths, disposable plastic gloves, coate
44、d tongs, or coated tweezers should normally be used. 2.1.6 Under a ventilated hood, remove any residual oils with a hydrocarbon solvent such as xylene, toluene, or 1,1,1 trichloroethane and rinse with anhydrous isopropyl alcohol. If oils are not present, cleaning with alcohol or acetone should be su
45、fficient. 2.1.7 Dry, measure, and weigh the coupons to within 0.1 mg. Record the mass, serial number, and exposed dimensions. Calculate the surface area (including the edges) and record. The areas covered by the coupon holder and shielded areas of flush-mounted coupons must be excluded. (For test ni
46、pples or other large corrosion test pieces, see Paragraph 3.6.) 2.1.8 Prior to shipment, store the individually packaged coupons in a closed container with indicating silica gel.(1) Coupons may be wrapped in paper or placed in envelopes impregnated with a vapor-phase corrosion inhibitor. 2.2 Procedu
47、re for Field Handling of Coupons Before and After Exposure 2.2.1 Prior to coupon installation, record the following information: coupon serial number, installation date, name of system, location of the coupon in the system (including fluid or vapor phase), and orientation of the coupon and holder. A
48、 typical corrosion coupon report is shown in Appendix A. 2.2.2 During installation, handle the coupon carefully to prevent contamination of the coupon surface. (See Paragraph 2.1.5.) 2.2.3 When the coupon is removed, record the coupon serial number, removal date, observations of any erosion or mechanical damage, and appearance of scale or corrosion product. Any other pertinent data such as shut-in time and changes
