As described in a previous report, a fungal consortium isolated from degraded polymeric materials was capable of growth on presterilized coupons of five composites, resulting in deep penetration into the interior of all materials within five weeks. Data describing the utilization of composite constituents as nutrients for the microflora are described in this article. Increased microbial growth was observed when composite extract was incubated with the fungal inoculum at ambient temperatures. Scanning electron microscopic observation of carbon fibers incubated with a naturally developed population of microorganisms showed the formation of bacterial biofilms on the fiber surfaces, suggesting possible utilization of the fiber chemical sizing as carbon and energy sources. Electrochemical impedance spectroscopy was used to monitor the phenomena occurring at the fiber-matrix interfaces. Significant differences were observed between inoculated and sterile panels of the composite materials. A progressive decline in impedance was detected in the inoculated panels. Several reaction steps may be involved in the degradation process. Initial ingress of water into the resin matrix appeared to be followed by degradation of fiber surfaces, and separation of fibers from the resin matrix. This investigation suggested that composite materials are susceptible to microbial attack by providing nutrients for growth.
Investigations were made using scanning electron microscopy to examine deeply etched specimens and electrolytically extracted carbides of as-cast high-speed steels. It is shown that eutectic carbides appear in three types of eutectic morphologies. A carbide “wall” exists around type I skeleton eutectic, and growth steps are evident on the top of carbide platelets of the lamellar type II eutectic. Type III generally develops a thick plate or bar form. The delta-eutectoid carbide attains a “bunched fiber” shape. Increasing molybdenum and decreasing tungsten leads to a change of eutectic carbide from skeleton to platelike and fiberlike morphologies. Vanadium not only promotes the formation of MC carbide, but also the formation of M2C carbide. It was noted to be unfavorable to the formation of M6C carbide, and increasing the vanadium content results in an increase in the size of eutectic and eutectoid carbides.
The alloy design of WC-10Co cemented carbide, modified with addition of a hard carbide phase, TiC, and with Ni and Mo in the binder phase, has been highlighted by the authors in a number of publications. The present article deals with the fine microstructural features of various phases in such cemented carbides. WC grains in all the investigated cemented carbide compositions appear to develop straight facets during sintering because of their anisotropic nature. In contrast, the TiC phase is characterized by its rounded shape. Dislocations are present in both WC and TiC grains, being of lesser density in the latter. The binder phase is always associated with stacking faults. The nature of the hard phase/binder interfaces has been found to be dependent on the binder phase chemistry. The observed changes in microstructures and mechanical properties have been correlated with the wettability and solubility of the hard phases in the binder melt, and with the different strengthening mechanisms in the binder phase.
NACE Recommended Practice RP-01-69, 'Control of External Corrosion on Underground or Submerged Metallic Piping Systems', contains criteria for the cathodic protection (CP) of steel structures in natural soil and water environments and these criteria have been widely accepted both by the owners of cathodically protected structures and by CP practitioners. Despite this, it has become increasingly apparent that many of the criteria as stated in the standard are in serious error with the fundamental science and in conflict with other standards and the interpretation of some regulatory agencies. Recent studies, which have appeared in the literature, further confirm that the criteria require revision to ensure that only polarized potentials are used in the criteria and, furthermore, that potential measurements are corrected for IR drop error.
The main pipeline runs from northwest Alberta, Canada to just south of Chicago, Illinois. Pipelines from British Columbia and Alberta feed gas into the main pipeline. A systematic approach to the design was undertaken. A computer analysis of the cathodic protection (CP) attenuation and voltage gradients was made. An analysis of subsurface geology was conducted for deep-anode groundbeds. This article discusses the systematic design process used for the CP application.
The design and investigation results of the protection system of the steel tubular piles of a 100,000 deadweight tonnage wharf is presented. The total protected area of the piles was 170,340 m2. Aluminum alloy sacrificial anodes of AZIC-H5 and AZIC-H7 were selected. Chemical compositions and chemical properties of the sacrificial anodes were tested before construction. The consumption of the sacrificial anodes installed on the carriage return platform, inside the oil loading platform, and outside the oil loading platform is less than that of the firefighting platform, compensator platform, and trestle. The protection potentials of all the measurement points satisfy the design requirement. The pile coating exhibited serious chalking, tarnish, and palling.
An investigation and testing were performed following a fracture event of a S13Cr-110 premium joint tubing string in a high-pressure, high-temperature well. Based on fracture analysis, fractography, and metallography, it was determined that the tubing failures were caused by stress corrosion cracking and corrosion fatigue. Analysis of the well depths of the failed tubes indicated that the load borne by the tubing string produced bending that resulted in tubing failure. Based on an analysis of the tubing string assembly process and the tubing structure, the failure occurred where the tubing string was weakest, which was the location of greatest flexibility.
Weldable martensitic 13% chromium stainless steels (WMSS) are used for mildly sour fowlines in the oil and gas industry. For most material selection and qualifcation programs for sour applications, the material is tested at the maximum design temperature and at ambient temperature. WMSS may be more susceptible to sulfde stress cracking below ambient temperature and current information in the literature is limited. Consequently, testing may show acceptable results, but in-service cracking could occur from exposure to temperatures below ambient. For subsea pipelines, the typical seabed temperature is ∼5 °C.
Fifty-five % Al-Zn coatings are several times more durable than zinc coating. At long exposure times in industrial and rural environments, corrosion rates become indistinguishable from aluminum coatings. Whereas all these coating provide sacrificial protection to exposed steel in chloride bearing marine environments, only zinc and 55% Al-Zn coatings provide edge protection in rural and industrial environments. Zinc corrosion products from preferential corrosion of the zinc rich portions of cored dendrites are trapped in the interdendritic interstices of an aluminum rich network, slowing further attack.
Fourteen year data for 90-10 and 70-30 cupronickel alloys exposed in sea water at the F. L. LaQue Corrosion Laboratory, Wrightsville Beach, North Carolina are reported. Corrosion rates for both alloys in quiet and flowing as well as in the tidal zone tended to become linear after the first 4 years' exposure. Initially, corrosion rates for 90-10 tended to be much higher in flowing than in either quiet or tidal zone exposures, but at 14 years, rates in all environments were about the same, 0. 05 mils per year. Similarly, 70-30 had high initial rates in flowing water, but at 14 years, rates were about the same for all three exposures, 0. 03 to 0. 08 mils per year.
A failure investigation was conducted to determine the cause and mechanism of a seam weld rupture of a 14-inch diameter API 5LX-46 electric resistance welding oil pipeline. Detailed laboratory investigations, including visual inspection, thickness measurement, elemental composition analysis, metallographic investigation, inclusion rating, hardness testing, tensile strength evaluation, fractography through scanning electron microscopy (SEM), were done to identify the causes and mechanism of the failure. A dye penetration test (DPT) was conducted over the entire sample, and no significant indications of surface cracks were observed. The prepared sample of the HAZ was etched with 2% Nital to reveal its microstructure. The sample exhibited banded ferrite and pearlite microstructure, typical of rolled carbon steel products with a large number of elongated and spherical inclusions/stringers. Visual inspection revealed that the opening of the failure had a smooth surface on either side of the edge without inward or outward bulging.
Recent developments associated with carbon capture and storage have significantly increased the use of carbon steel pipelines for the transport of supercritical carbon dioxide (CO). These. pipelines are not specifically covered by ANSI/NACE MR0175/ISO 15156, Which applies to oil and gas production; however, it is prudent to consider the possible risks of sulfide stress cracking and hydrogen-induced cracking that can arise in the presence of a liquid water phase.
Results of 16-year tests of metals in tropical sea water total and intermittent immersion and atmospheres are reported. Data are tabulated on carbon and low-alloy steels, alpha and beta brasses, bronzes, NiCu and CuNi, austenitic stainless steels, and commercially pure Al, Cu, Ni, Pb, and Zn, both as single metals and in many combinations of couples both in water and atmospheres. Data recorded include both weight loss and tensile strength as well as statistical summaries of pitting. While many of the data have been reported previously, this report gives first information on cast bronzes, and atmospheric exposures of weathering steel. Some anomalies are reported and bimetallic couple results are reported for the first time also. In addition to confirmation of results from other studies, some of the data contradict or modify conclusions reached earlier for the same materials, especially with respect to exposures elsewhere than in the tropics. This is the final report on the project.
Using the go/no-go temperature for localized corrosion initiation as a criterion, a number of commercial stainless steels have been evaluated for pitting and crevice corrosion. The results, when plotted as a function of molybdenum content in the alloy, fall in a series of families which had been found previously for both experimental and commercial alloys. The results apply only to localized corrosion (pitting or crevice corrosion) in oxidizing chloride solutions.
This paper reviews basic cooling water corrosion, scaling, and fouling mechanisms and illustrates how operating parameters and control procedures have changed to meet the requirements of new technology. Modern cooling water programs are reviewed and needs for new technology are discussed.
Electrochemical cyclic potentiodynamic polarization experiments were performed on six types of alloys to evaluate their susceptibility to localized corrosion in aqueous environments relevant to the potential underground, high-level nuclear waste repository. The effects of chloride ion (Cl-) concentration, pH, temperature, and electrochemical potential scan rate on the pitting/crevice corrosion behavior of these materials were investigated. The results indicated that alloys 825, G-3, and G-30 suffered from pitting and crevice corrosion in all tested environments. Alloy C-4 showed localized attack in 90 degrees C brines, but alloys C-22 and Ti Grade-12 were immune to localized corrosion under all experimental conditions studied.
Moisture on a metal surface generally is considered a major problem for coatings application, because it is a key cause of poor adhesion and other coating system defects. However, moisture-cure urethane coatings actually rely on atmospheric and surface moisture to form solid paint films. This characteristic makes them very surface-tolerant. As a result, moisture-cure urethanes are ideal for damp surfaces and low-temperature applications, extending the painting season for contractors and improving productivity by eliminating downtime. Developed similar to 30 years ago, primarily for offshore applications, moisture-cure urethanes initially showed great promise. However, original formulations posed daunting limitations on recoatability and stability, and their high cost made the coatings impractical. Only in the past decade have technological advances made moisture-cure urethanes viable and valuable alternatives in the industrial coatings arsenal of corrosion preventing weapons.
Long-term corrosion test results define the corrosion resistance and limits of Ta and its alloy as a material of construction in sulfuric applications. Isocorrosion diagrams for technical sulfuric acid (H 2SO 4) and H 2SO 4 with residual nitrates were established. The data demonstrate that Ta-2.5% W can be used in 96 wt% H 2SO 4 up to 200°C. Comparison of Ta and Ta-2.5% W shows that the alloy performs better than the metal, particularly in H 2SO 4 containing oxidizing impurities such as nitrates.
This article describes the failure analysis of Ni 200 (UNS N02200) heat exchanger piping in a chlorine and alkali factory. Intergranular corrosion in a chloride environment caused the failure. Three candidate replacement alloys were selected and tested. AL 29-4 (UNS S44700) alloy was found to have the best corrosion resistance and was chosen to replace N02200 in this environment. At present, this alloy piping has been used for more than 4 years without any evident corrosion.
Being a cathodic protection corrosionist is a lot like being a detective. It is necessary to examine all the evidence when solving a mystery. Sometimes it is necessary to establish a stakeout. That's what was done to find the source of intermittent shorts in this incident, Careful use of instrumentation, data analysis, and observation solved the problem.
The 2005 NACE corrosion career survey of the US and Canadian corrosion professionals addressing their educational qualifications, work functions and annual compensation is discussed. The largest percentage of US NACE members have bachelor's degrees, followed by high school diplomas, associate's degrees, master's degrees, doctorates, and post-doctorates. In Canada, 38% of members have bachelor's degrees, followed by associate's degrees, high school diplomas, master's degrees, doctorates, and post-doctorates. More than 30% of US and Canadian members work for companies involved in operating and maintaining oil and gas pipelines and storage tanks.
Liquid epoxy coatings have many uses in the pipeline industry. This article discusses the technology of these coatings and presents both the advantages and limitations of this material. Typical applications for liquid epoxy coatings are presented.
Materials Performance (MP), a corrosion prevention and control magazine has requested corrosion professionals to provide technical articles, news items, and cover photos for its year 2007 issues. Some of the topics of technical articles include description of a new or improved means of solving a corrosion problem and describing a field or failure analysis that illustrates the rationale in materials selection, control methods, and inspection technology. The magazine requires that articles based on conference papers must be submitted as double-spaced manuscripts, conforming to its guidelines. Conference papers that have lengthy abstracts, text, and numerous tables and figures should be reduced to fit the space available in MP. It also requires that news items should be brief announcements of significant new findings, technical trends, company news, and description of innovative products or systems.
The results of the 2008 NACE International Corrosion Career Survey including a study of long-term involvement in corrosion, education and training, and career satisfaction and challenges, are presented. The survey found that the average salary for corrosion professionals is $88,354 and the average Canadian compensation in taxable income is $94,357. 58% of the professionals are found to be in the corrosion industry for 10 or more years and 30% for 20 or more years. The US corrosion professionals recognize the value of corrosion education and training with 84% attending educational and course-based training. The corrosion professionals also highlighted the importance of more advancement opportunities, larger budget for corrosion control, improved access to corrosion control technologies, and improved relationship with upper management.
