1、 Standard Test Method Detection, Testing, and Evaluation of Microbiologically Influenced Corrosion (MIC) on External Surfaces of Buried Pipelines This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its accept
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11、Houston, Texas 77084-4906 +1 281/228-6200 ISBN 1-57590-206-0 2006, NACE International NACE Standard TM0106-2006 Item No. 21248 TM0106-2006 NACE International i _ Foreword Microbiologically influenced corrosion (MIC) is an aggressive type of corrosion caused by the presence or activities of microorga
12、nisms. Microbiologically mediated reactions can alter both rates and types of electrochemical reactions. These reactions do not result in a unique manifestation of corrosion. Rather, microbial activities can produce a broad range of outcomes including pitting, crevice corrosion, differential aeratio
13、n cells, metal concentration cells, selective dealloying, enhanced erosion, and enhanced galvanic corrosion. Therefore, MIC investigations require microbiological, chemical, and metallurgical testing for proper diagnosis. The conclusion that MIC has taken place should be based on the preponderance o
14、f circumstantial evidence. Microorganisms are often resistant to many control methods and can be a serious threat to pipelines, especially those that have coating or cathodic protection (CP) systems that are not properly maintained. This NACE standard test method is for ferrous-based metal pipeline
15、facilities and describes types of microorganisms, mechanisms by which MIC occurs, methods of testing for the presence of bacteria, research results, and interpretation of testing results. Sections 1 through 4 of this standard discuss the technical aspects of MIC. Sections 5 through 7 discuss field e
16、quipment and testing procedures. Media and techniques that can be used for testing are outlined in Appendix A. This standard is intended for use by pipeline operators, pipeline service providers, government agencies, and any other persons or companies involved in planning or managing pipeline integr
17、ity. Portions of Sections 3 and 4 of this standard are excerpted from Peabodys Control of Pipeline Corrosion, Chapter 14“Microbiologically Influenced Corrosion,”1and enclosed in quotation marks. This standard was prepared by Task Group (TG) 237 on Microbiologically Influenced Corrosion on External S
18、urfaces of Buried Pipelines: Detection, Testing, and EvaluationStandard. TG 237 is administered by Specific Technology Group (STG) 35 on Pipelines, Tanks, and Well Casings and is sponsored by STG 60 on Corrosion Mechanisms. This standard is issued by NACE International under the auspices of STG 35.
19、In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph 7.4.1.9. Shall and must are used to state mandatory requirements. The term should is used to state something considered good
20、and is recommended but is not mandatory. The term may is used to state something considered optional. _ TM0106-2006 ii NACE International _ NACE International Standard Test Method Detection, Testing, and Evaluation of Microbiologically Influenced Corrosion (MIC) on External Surfaces of Buried Pipeli
21、nes Contents 1. General 1 2. Definitions 1 3. Introduction 3 4. MIC of Pipelines 5 5. Sampling Equipment . 6 6. Sampling and Testing Procedures 7 7. Interpretation . 11 References 11 Bibliography 13 Nonmandatory Appendix A: Media Specifications for Each Type of Organism 13 Nonmandatory Appendix B: D
22、ilution Procedure . 17 Nonmandatory Appendix C: Site Inspection and Testing . 19 Figure 1: Examples of Pit Morphology 8 Table A1: Media Specifications for Aerobic Heterotrophic Bacteria . 13 Table A2: Postgates B MediumLactate Based. 14 Table A3: Media Specifications for Various Types of Phenol Red
23、Broth 15 Table A4: Specifications for an Iron-Reducing Bacteria Medium . 17 Table B1: Number of Target Organisms Based on Number of Positive Bottles. 18 Table C1: Site Inspection and Testing Checklist 19 _ TM0106-2006 NACE International 1 _ Section 1: General 1.1 This standard describes types of mic
24、roorganisms, mechanisms by which MIC occurs, methods of testing for the presence of bacteria, research results, and interpretation of testing results for external surfaces of buried, ferrous-based metal pipelines and related components. 1.2 Appendixes are included for media specifications (nonmandat
25、ory Appendix A), dilution procedures (nonmandatory Appendix B), and site inspection and testing (nonmandatory Appendix C). 1.3 All applicable safety and environmental codes, rules, and regulations must be followed when using this standard. _ Section 2: Definitions Abiotic: The absence of biological
26、factors. Acid-Producing Bacteria (APB): Aerobic or anaerobic bacteria that produce organic acids as an end product of their metabolism. A few organisms, e.g., Thiobacillus, are also capable of producing mineral acids (typically under aerobic conditions), which can result in lower pH levels (4.0 or l
27、ower) than organic acids. Aeration: (1) Exposing to the action of air. (2) Causing air to bubble through. (3) Introducing air into a solution by spraying, stirring, or similar method. (4) Supplying or infusing with air, as in sand or soil. (5) Charging a liquid with some gas, such as water with carb
28、on dioxide (soda water). (6) The introduction of air into the pulp in a flotation cell to form air bubbles. Aerobic (aerobe) Bacteria: An organism that uses oxygen as the final electron acceptor in metabolism. Anaerobic (anaerobe) Bacteria: Free of air or uncombined oxygen. For the purpose of this s
29、tandard, an organism that does not require oxygen for metabolism. Assimilatory: The conversion via cellular processes of simple molecules into the complex components of the microbial cell, e.g., assimilatory sulfate or nitrate reduction. Autoclave: A pressurized, steam-heated vessel used for sterili
30、zation. Basal: The minimal level for, or essential for maintenance of, vital activities of an organism, such as basal metabolism. Biofilm: Microbial growth at an interface in which individual cells are bound within a matrix of extracellular polymeric materials. Biotic: The presence of biological fac
31、tors. Carbohydrate: Any of the group of organic compounds composed of carbon, hydrogen, and oxygen, including sugars, starches, and celluloses. Cathodic Protection: A technique to reduce the corrosion of a metal surface by making that surface the cathode of an electrochemical cell. Coating: A liquid
32、, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative, or functional adherent film. Coating System: The complete number and types of coats applied to a substrate in a predetermined order. (When used in a broader sense, surface pre
33、paration, pretreatments, dry film thickness, and manner of application are included.) Culture Medium: A sterile solution or other substrate that is formulated to promote the growth of a particular type or group of microorganisms. Deaeration: Removal of oxygen or air from a system or substance, as fr
34、om feedwater or food. Dielectric: A nonconductor of electricity. The term is usually applied where electric fields are possible, as with the insulating material between the plates of a capacitor. Dielectric Coating: A coating that does not conduct electricity. Disbondment: The loss of adhesion betwe
35、en a coating and the substrate. Dissimilatory: Metabolic reaction in which a reductant is used as an electron acceptor and not incorporated into the cell, e.g., dissimilatory sulfate or nitrate reduction; metabolic changes that convert complex molecules into simple ones. Facultative: Capable of grow
36、ing either with or without the presence of a specific environmental factor, e.g., oxygen. Fungi: Nucleated, usually filamentous, spore-bearing parasitic organisms devoid of chlorophyll, including molds, mildews, smuts, mushrooms, yeast, etc. TM0106-2006 2 NACE International Growth: Increase in the q
37、uantity of metabolically active protoplasm, accompanied by an increase in cell number, cell size, or both. Growth Medium: See Culture Medium. Heterotrophic: An organism that obtains nourishment from the ingestion and breakdown of organic matter. Holiday: A discontinuity in a protective coating that
38、exposes unprotected surface to the environment. Inoculum: A small quantity of bacteria used to start a new culture. Inorganic Acid: A compound composed of hydrogen and a nonmetal element or radical; examples are hydrochloric acid (HCl) and sulfuric acid (H2SO4). Isotonic: Having uniform tension of a
39、 solution; having the same osmotic pressure as the fluid phase of a cell or tissue. Metal-Reducing Bacteria (MRB): Bacteria that in direct contact with solid iron (Fe+3) and manganese (Mn+4) oxides produce soluble ions (Fe+2and Mn+2) resulting in dissolution of surface oxides and localized corrosion
40、.1Microaerophilic: Pertaining to those microorganisms requiring free oxygen but in very low concentration for optimum growth. Microbiologically Influenced Corrosion (MIC): Corrosion brought about by the presence or activities of microorganisms in biofilms on the surface of the corroding material. Ma
41、ny materials, including most metals and some nonmetals, can be degraded in this manner. Microorganism: An organism of microscopic or ultramicroscopic size. Monosaccharide: A carbohydrate that cannot be hydrolyzed to a simpler carbohydrate. Morphology: A branch of biology that deals with structure an
42、d form of an organism at any stage of its life history. Motile: Exhibiting or capable of movement. Obligate: Can only grow with or without the presence of a specific environmental factor; e.g., obligate anaerobes cannot grow if oxygen is present in the local environment. Organic Acids: Weak acids th
43、at contain carbon (correctly classified as carboxylic acids because they contain a carboxyl group, -COOH) and are the end product of metabolism by a variety of microorganisms, e.g., acetic, formic, lactic, etc. Also called short-chain fatty acids. Organism: A complex structure of interdependent and
44、subordinate elements whose relations and properties are largely determined by their function as a whole. Oxidation-Reduction Potential: The potential of a reversible oxidation-reduction electrode measured with respect to a reference electrode, corrected to the hydrogen electrode, in a given electrol
45、yte. Permeation: The migration of water from the soil through the coating to the pipe surface by diffusion. Phosphate Buffer: Solution made of dibasic potassium phosphate (K2HPO4) and sodium phosphate (Na2HPO4). Pipe-to-Soil Potential: See Structure-to-Electrolyte Potential. Polysaccharide: A carboh
46、ydrate composed of many monosaccharides. Redox potential (Eh): See Oxidation-Reduction Potential. Ringers Solution: An aqueous solution of chlorides that is isotonic to animal tissues. Sterile: (1) Free of any living microorganisms. (2) Not introducing microorganisms that are foreign to the host bod
47、y or subject under study. Structure-to-Electrolyte Potential: The potential difference between the surface of a buried or submerged metallic structure and the electrolyte that is measured with reference to an electrode in contact with the electrolyte. Substratum: A solid surface; often refers to a s
48、urface colonized by microorganisms. Sulfate-Reducing Bacteria (SRB): A group of anaerobic bacteria that perform dissimilatory reduction of sulfate, resulting in sulfide formation. Tenting: A tent-shaped void formed along the girth weld or longitudinal seam-weld reinforcement in a pipe when the external coating is not in continuous intimate contact with the pipe and weld surfaces. Water Leaching: The removal of soluble constituents from a coating by water. TM010
