1、Designation: G205 10Standard Guide forDetermining Corrosivity of Crude Oils1This standard is issued under the fixed designation G205; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenthese
2、s indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide presents some generally accepted laboratorymethodologies that are used for determining the corrosivity ofcrude oil.1.2 This guide does not cover
3、 detailed calculations andmethods, but rather a range of approaches that have foundapplication in evaluating the corrosivity of crude oil.1.3 Only those methodologies that have found wide accep-tance in crude oil corrosivity evaluation are considered in thisguide.1.4 This guide does not address the
4、change in oil/water ratiocaused by accumulation of water at low points in a pipelinesystem.1.5 This guide is intended to assist in the selection ofmethodologies that can be used for determining the corrosivityof crude oil under conditions in which water is present in theliquid state (typically up to
5、 100C). These conditions normallyoccur during oil and gas production, storage, and transportationin the pipelines.1.6 This guide does not cover the evaluation of corrosivityof crude oil at higher temperatures (typically above 300C) thatoccur during refining crude oil in refineries.1.7 This guide inv
6、olves the use of electrical currents in thepresence of flammable liquids. Awareness of fire safety iscritical for the safe use of this guide.1.8 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.9 This standard does not purport
7、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.2. Referenced Documents2.1 ASTM Standards:2D96 Tes
8、t Methods for Water and Sediment in Crude Oil byCentrifuge Method (Field Procedure)3D473 Test Method for Sediment in Crude Oils and Fuel Oilsby the Extraction MethodD665 Test Method for Rust-Preventing Characteristics ofInhibited Mineral Oil in the Presence of WaterD724 Test Method for Surface Wetta
9、bility of Paper (Angle-of-Contact Method)3D1125 Test Methods for Electrical Conductivity and Resis-tivity of WaterD1129 Terminology Relating to WaterD1141 Practice for the Preparation of Substitute OceanWaterD1193 Specification for Reagent WaterD4006 Test Method for Water in Crude Oil by Distillatio
10、nD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4377 Test Method for Water in Crude Oils by Potentio-metric Karl Fischer TitrationG1 Practice for Preparing, Cleaning, and Evaluating Corro-sion Test SpecimensG31 Practice for Laboratory Immersion Corrosion Testingof MetalsG111 G
11、uide for Corrosion Tests in High Temperature orHigh Pressure Environment, or BothG170 Guide for Evaluating and Qualifying Oilfield andRefinery Corrosion Inhibitors in the LaboratoryG184 Practice for Evaluating and Qualifying Oil Field andRefinery Corrosion Inhibitors Using Rotating CageG193 Terminol
12、ogy and Acronyms Relating to CorrosionG202 Test Method for Using Atmospheric Pressure Rotat-ing Cage1This guide is under the jurisdiction of ASTM Committee G01 on Corrosion ofMetals and is the direct responsibility of Subcommittee G01.05 on LaboratoryCorrosion Tests.Current edition approved Sept. 1,
13、 2010. Published October 2010. DOI: 10.1520/G020510.2For referenced ASTM standards, visit the ASTM website, 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.3Withdraw
14、n. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.2 ISO Standard:4ISO 6614 Petroleum productsDetermination of WaterSeparability of Petroleum Oils a
15、nd Synthetic Fluids2.3 NACE Standard:5TM0172 Standard Test Method Determining CorrosiveProperties of Cargoes in Petroleum Product Pipelines3. Terminology3.1 DefinitionsThe terminology used herein, if not spe-cifically defined otherwise, shall be in accordance with GuideG170, Terminology and Acronyms
16、 G193, and TerminologyD1129. Definitions provided herein and not given in GuideG170, Terminology and Acronyms G193, and TerminologyD1129 are limited only to this guide.3.2 Definitions of Terms Specific to This Standard:3.2.1 emulsion, ntwo-phase immiscible liquid system inwhich one phase is disperse
17、d as droplets in the other phase.3.2.2 emulsion-inversion point, npercentage of water atwhich a water-in-oil (W/O) emulsion converts into an oil-in-water (O/W) emulsion.3.2.3 wettability, ntendency of a liquid to wet or adhereon to a solid surface.3.3 Acronyms:CO2= Carbon dioxideEIP = Emulsion inver
18、sion pointH2S = Hydrogen sulfideKOH = Potassium hydroxideNaCl = Sodium chlorideNa2CO3= Sodium carbonateNaHCO3= Sodium bicarbonateNaOH = Sodium hydroxideNa2S = Sodium sulfideO/W = Oil-in-waterW/O = Water-in-oil4. Summary of Guide4.1 This guide describes methods for determining the cor-rosivity of cru
19、de oils by a combination of three properties: (1)the emulsion of the oil and water, (2) the wettability of the steelsurface, and (3) the corrosivity of water phase in the presenceof oil.4.2 Conductivity of emulsion can be used to determine thetype of emulsion: oil in water (O/W) or water in oil (W/O
20、). Theconductivity of the O/W emulsion (in which water is thecontinuous phase) is high. The conductivity of the W/Oemulsion (in which oil is the continuous phase) is low.4.3 The wettability of a steel surface is determined usingtwo methods: (1) contact angle method and (2) spreadingmethod.4.4 The co
21、rrosiveness of water phase in the presence ofcrude oil can be determined using several methods.5. Significance and Use5.1 In the absence of water, the crude oil is noncorrosive.The presence of sediment and water makes crude oil corrosive.Test Methods D96, D473, D4006, and D4377 provide methodsfor th
22、e determination of the water and sediment content ofcrude oil.5.2 The corrosivity of crude oil containing water can bedetermined by a combination of three properties (Fig. 1)(1)6:the type of emulsion formed between oil and water, thewettability of the steel surface, and the corrosivity of waterphase
23、 in the presence of oil.5.3 Water and oil are immiscible but, under certain condi-tions, they can form emulsion. There are two kinds of emul-sion: O/W and W/O. W/O emulsion (in which oil is thecontinuous phase) has low conductivity and is thus lesscorrosive; whereas O/W (in which water is the contin
24、uousphase) has high conductivity and, hence, is corrosive (seeISO 6614)(2). The conductivities of various liquids are pro-vided in Table 1(3). The percentage of water at which W/Oconverts to O/W is known as the emulsion inversion point(EIP). EIP can be determined by measuring the conductivity ofthe
25、emulsion. At and above the EIP, a continuous phase ofwater or free water is present. Therefore, there is a potential forcorrosion.5.4 Whether water phase can cause corrosion in the pres-ence of oil depends on whether the surface is oil wet (hydro-phobic) or water wet (hydrophilic) (4-8). Because of
26、higherresistance, an oil-wet surface is not susceptible to corrosion,but a water-wet surface is. Wettability can be characterized bymeasuring the contact angle or the conductivity (spreadingmethod).5.4.1 In the contact angle method, the tendency of water todisplace hydrocarbon from steel is measured
27、 directly byobserving the behavior of the three phase system. The contactangle is determined by the surface tensions (surface freeenergies) of the three phases. A hydrocarbon-steel interfacewill be replaced by a water-steel interface if this action willresult in an energy decrease of the system. To
28、determinewhether the surface is oil wet, mixed wet, or water wet, theangle at the oil-water-solid intersection is observed and mea-sured.5.4.2 In the spreading method of determining wettability,the resistance between steel pins is measured. If a conductingphase (for example, water) covers (wets) the
29、 distance betweenthe pins, conductivity between them will be high. On the otherhand, if a nonconducting phase (for example, oil) covers (wets)the distance between the pins, the conductivity between themwill be low.5.5 Dissolution of ingredients from crude oils may alter thecorrosiveness of the aqueo
30、us phase. Based on how the corro-sivity of the aqueous phase changes in its presence, a crude oilcan be classified as corrosive, neutral, inhibitory, or preventivecrude. Corrosiveness of the aqueous phase in the presence of4Available from the American National Standards Institute, 25 W. 43rd St., Ne
31、wYork, NY 10036.5Available from the NationalAssociation of Corrosion Engineers, 1440 S. CreekDr., Houston, TX 77084-4906.6The boldface numbers in parentheses refer to a list of references at the end ofthis standard.G205 102oil can be determined by methods described in Test MethodD665, Guide G170, Pr
32、actice G184, Test Method G202, andNACE TM0172.6. Materials6.1 Methods for preparing coupons and probes for tests andfor removing coupons after the test are described in PracticeG1. Standard laboratory glassware should be used for weighingand measuring reagent volumes.6.2 The coupons/probes should be
33、 made of the field material(such as carbon steel) and have the same metallographicstructure as that used in the service components. The probes forwettability and EIP measurements should be ground to asurface finish of 600 grit. Preparation of coupons for corrosionmeasurements is described in Guide G
34、170, Practice G184, andTest Method G202.7. Preparation of Test Solutions7.1 Oil should be obtained from the field that is beingevaluated. Practice D4057 provides guidelines for collectingcrude oil. It is important that live fluids do not containFIG. 1 Predicting Influence of Crude Oil on the Corrosi
35、vity of Aqueous PhaseG205 103externally added contaminants, for example, corrosion inhibi-tors, biocides, and surfactants. A water sample should also beobtained from the field. A synthetic aqueous solution could beused; the composition of which, however, should be based onfield water analysis. Alter
36、natively, standard 3 % brine orsynthetic brine (of a composition provided in Practice D1141)may be used. Their composition should be specified in thework plan and recorded in the laboratory logbook. Thesolutions should be prepared following good laboratory prac-tice. The solutions should be prepared
37、 using reagents (inaccordance with Test Method G202) and deionized water (inaccordance with Specification D1193).7.2 The solutions (oil and water phases) should be deaeratedby passing nitrogen (or any other inert gas) and kept underdeaerated conditions. Solutions should be transferred withminimal co
38、ntact with air. Procedures to transfer the solutionsare described in Test Method G202.7.3 Procedures to deoxygenate and saturate the solutionswith acid gases are presented in Test Method G202.Tosimulate field operating conditions, the solution is often re-quired to be saturated with acid gases such
39、as hydrogen sulfide(H2S) and carbon dioxide (CO2). H2S and CO2are corrosivegases. H2S is poisonous and shall not be released to theatmosphere. The appropriate composition of gas can be ob-tained by mixing H2S, CO2, and methane streams from thestandard laboratory gas supply. Nitrogen or any other ine
40、rt gascan be used as a diluent to obtain the required partial pressuresof the corrosive gases. Alternatively, gas mixtures of theappropriate compositions can be purchased from suppliers ofindustrial gases. The composition of gas depends on the fieldgas composition. The oxygen concentration in soluti
41、on de-pends on the quality of gases used to purge the solution. Theoxygen content of nitrogen or the inert gas should be less then10 ppm by volume. Leaks through the vessel, tubing, and jointsshould be avoided.7.4 The test vessels should be heated slowly to avoidoverheating. The thermostat in the he
42、ater or thermostatic bathshould be set not more than 20C above the solution tempera-ture until the test temperature is reached. The pressure in thevessel should be monitored during heating to make sure it doesnot exceed the relief pressure. If necessary, some of the gas inthe vessel may be bled off
43、to reduce the pressure. The testtemperature should be maintained within +2C of the specifiedtemperature. Once the test temperature is reached, the testpressure should be adjusted to the predetermined value. Thepressure should be maintained within +10 % of the specifiedvalue for the duration of the t
44、est.7.5 Ageneral procedure to carry out experiments at elevatedpressure and elevated temperature is described in Guide G111.For elevated temperature and elevated pressure experimentsusing individual gases, first the autoclave is pressurized withH2S to the required partial pressure and left for 10 mi
45、n. If thereis a decrease of pressure, the autoclave is repressurized. Thisprocess is repeated until no further pressure drop occurs. Then,the autoclave is pressurized with CO2by opening the CO2gascylinder at a pressure equal to the CO2+H2S partial pressureand left for 10 min. If there is a decrease
46、in pressure, theautoclave is repressurized with CO2gas. This process isrepeated until no further pressure drop is observed. Finally, theautoclave is pressurized with an inert gas (for example,methane) by opening the appropriate cylinder at the total gaspressure at which the experiments are intended
47、to be carriedout.8. Laboratory Methodologies8.1 Determination of Emulsion Type:8.1.1 A schematic diagram of the equipment used fordetermining the emulsion type is presented in Figs. 2 and 3.The apparatus consists of an experimental section (Fig. 3), areservoir, a circulating pump, and a flow control
48、ler.8.1.2 The experimental section (Fig. 3) is a 15-cm-longhorizontal pipe section of 2.5 cm in diameter containing twovertically placed measuring pins (typically made from carbonsteel). The distances between the pins can be varied with ascrew arrangement. For optimal measurements, a pin distanceof
49、0.25 cm is suggested.8.1.3 The reservoir (typically 7-L capacity) may be anautoclave (for higher pressure measurements) or a glasscontainer (for atmospheric pressure measurements). The topcover of the reservoir is fitted with an inlet, an outlet, and animpeller. For higher pressure experiments, the reservoir is alsofitted with a pressure gauge to monitor the pressure. Theimpeller should be capable of rotating at annular rotationspeeds higher than 1000 rpm.8.1.4 The circulating pump is used to circulate the emulsionbetween the reservoir and the experimental section. The pum
