A flanged 100 mm (4 in.) diam low-carbon steel spool piece lined with Teflon was removed from a sulfuric acid denitrification system after cracks were observed in the painted coating. Visual and microstructural examination along with SEM fractography revealed scaled iron oxides on all opened crack surfaces. The surfaces had a faceted morphology, indicating intergranular fracture. Cracks originated at the interface between the tube and the Teflon liner Corrosion products were found caked into the intergranular region between the liner and the spool. The portion of the liner that had been exposed to the process stream was discolored. Failure of the spool was attributed to stress-corrosion cracking promoted by the presence of nitrates. Nitric acid contaminant in the sulfuric acid stream had diffused through the liner and accumulated in the annular space. Use of a liner that is more impermeable to the diffusion of ionic species was recommended.

This article provides an overview of the electrochemical nature of corrosion and analyzes corrosion-related failures. It describes corrosion failure analysis and discusses corrective and preventive approaches to mitigate corrosion-related failures of metals. These include: change in the environment; change in the alloy or heat treatment; change in design; use of galvanic protection; use of inhibitors; use of nonmetallic coatings and liners; application of metallic coatings; use of surface treatments, thermal spray, or other surface modifications; corrosion monitoring; and preventive maintenance.

Polymer materials are key building blocks of the modern world, commonly used in packaging, automobiles, building materials, electronics, telecommunications, and many other industries. These commercial applications of polymeric materials would not be possible without the use of additives. This article is divided into five sections: mechanical property modifiers, physical property modifiers, biological function modifiers, processing aids, and colorants. It describes three classes of additives that are used to inhibit biological activity, six classes of mechanical property modifiers, three classes of physical property modifiers, and two classes of both colorants and processing aids.

In 1975, a manufacturer was awarded a contract to produce modular air-traffic control towers for the U.S. Navy. The specifications called for painted steel siding, but the manufacturer convinced the Navy to substitute aluminum-bonded-to-plywood panels that were provided by a supplier. In less than one year, the panels began to delaminate and the aluminum began to crack. It was found that the failure was the result of chloride-induced intergranular corrosion caused by chemicals in the adhesive and excessive moisture in the wood introduced during manufacturing.

Corrosion is the deterioration of a material by a reaction of that material with its environment. The realization that corrosion control can be profitable has been acknowledged repeatedly by industry, typically following costly business interruptions. This article describes the electrochemical nature of corrosion and provides the typical analysis of environmental- and corrosion-related failures. It presents common methods of testing of laboratory corrosion and discusses the processes involved in the prevention of environmental- and corrosion-related failures of metals and nonmetals.

The failure of a 45 Mg (50 ton) rail crane bolster was investigated. Spectrochemical analysis indicated that the material was a 0.25C-1.24Mn-0.62Cr-0.24Mo cast steel. SEM examination revealed the presence of fatigue, as well as intergranular and ductile fractures. Microstructural analysis focused on an area where an antisway device had been welded to the structure and revealed the presence of coarse, untempered martensite that had resulted from faulty weld repair techniques. It was suggested that the use of proper welding procedures, including preheating and postheating, would have prevented the failure.

This article presents a general overview of outdoor weather aging factors, their effects on the performance of polymeric materials, and the accelerated test methods that can be used to investigate those effects. These test methods are used to characterize material performance when subjected to specific, often controlled, and well-defined factors. The article also presents an overview of weathering instrument types that simulate outdoor stress factors.

This article focuses on the mechanisms of microbially induced or influenced corrosion (MIC) of metallic materials as an introduction to the recognition, management, and prevention of microbiological corrosion failures in piping, tanks, heat exchangers, and cooling towers. It discusses the degradation of various protective systems, such as corrosion inhibitors and lubricants. The article describes the failure analysis of steel, iron, copper, aluminum, and their alloys. It also discusses the probes available to monitor conditions relevant to MIC in industrial systems and the sampling and analysis of conditions usually achieved by the installation of removable coupons in the target system. The article also explains the prevention and control strategies of MIC in industrial systems.

High-level radioactive wastes generated during the processing of nuclear materials are kept in large underground storage tanks made of low-carbon steel. The wastes consist primarily of concentrated solutions of sodium nitrate and sodium hydroxide. Each of the tanks is equipped with a purge ventilation system designed to continuously remove hydrogen gas and vapors without letting radionuclides escape. Several intergranular cracks were discovered in the vent pipe of one such system. The pipe, made of galvanized steel sheet, connects to an exhaust fan downstream of high-efficiency particulate air filters. The failure analysis investigation concluded that nitrate-induced stress-corrosion cracking was the cause of the failure.

This article first provides an overview of the types of mechanical fasteners. This is followed by sections providing information on fastener quality and counterfeit fasteners, as well as fastener loads. Then, the article discusses common causes of fastener failures, namely environmental effects, manufacturing discrepancies, improper use, or incorrect installation. Next, it describes fastener failure origins and fretting. Types of corrosion in threaded fasteners and their preventive measures are then covered. The performance of fasteners at elevated temperatures is addressed. Further, the article discusses the types of rivet, blind fastener, and pin fastener failures. Finally, it provides information on the mechanism of fastener failures in composites.

This article addresses the effects of damage to equipment and structures due to explosions (blast), fire, and heat as well as the methodologies that are used by investigating teams to assess the damage and remaining life of the equipment. It discusses the steps involved in preliminary data collection and preparation. Before discussing the identification, evaluation, and use of explosion damage indicators, the article describes some of the more common events that are considered in incident investigations. The range of scenarios that can occur during explosions and the characteristics of each are also covered. In addition, the article primarily discusses level 1 and level 2 of fire and heat damage assessment and provides information on level 3 assessment.

This article focuses on the mechanisms of microbiologically influenced corrosion as a basis for discussion on the diagnosis, management, and prevention of biological corrosion failures in piping, tanks, heat exchangers, and cooling towers. It begins with an overview of the scope of microbial activity and the corrosion process. Then, various mechanisms that influence corrosion in microorganisms are discussed. The focus is on the incremental activities needed to assess the role played by microorganisms, if any, in the overall scenario. The article presents a case study that illustrates opportunities to improve operating processes and procedures related to the management of system integrity. Industry experience with corrosion-resistant alloys of steel, copper, and aluminum is reviewed. The article ends with a discussion on monitoring and preventing microbiologically influenced corrosion failures.

Chemical analysis is a critical part of any failure investigation. With the right planning and proper analytical equipment, a myriad of information can be obtained from a sample. This article presents a high-level introduction to techniques often used for chemical analysis during failure analysis. It describes the general considerations for bulk and microscale chemical analysis in failure analysis, the most effective techniques to use for organic or inorganic materials, and examples of using these techniques. The article discusses the processes involved in the chemical analysis of nonmetallics. Advances in chemical analysis methods for failure analysis are also covered.

This article briefly introduces the concepts of failure analysis, including root-cause analysis (RCA), and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. It initially provides definitions of failure on several different levels, followed by a discussion on the role of failure analysis and the appreciation of quality assurance and user expectations. Systematic analysis of equipment failures reveals physical root causes that fall into one of four fundamental categories: design, manufacturing/installation, service, and material, which are discussed in the following sections along with examples. The tools available for failure analysis are then covered. Further, the article describes the categories of mode of failure: distortion or undesired deformation, fracture, corrosion, and wear. It provides information on the processes involved in RCA and the charting methods that may be useful in RCA and ends with a description of various factors associated with failure prevention.

The goal of using nondestructive evaluation (NDE) in conjunction with failure analysis is to obtain the most comprehensive set of data in order to characterize the details of the damage and determine the factors that allowed the damage to occur. The NDE results can be used to determine optimal areas upon which to focus for sectioning and metallography in order to further investigate the condition of the component. This article provides information on the inspection method available for failure analysis, including standard methods such as visual testing, penetrant testing, and magnetic particle testing. It covers the effects of various factors on the properties of the part that may impact failure analysis, describes the characterization of damage modes and crack sizes, and finally discusses the processes involved in application of NDE results to failure analysis.

The Rocky Point Viaduct, located near Port Orford, OR, was replaced after only 40 years of service. A beam from the original viaduct was studied in detail to determine the mechanisms contributing to severe corrosion damage to the structure. Results are presented from the delamination survey, potential and corrosion mapping, concrete chemistry, and concrete physical properties. The major cause of corrosion damage appears to have been the presence of both pre-existing and environmentally-delivered chlorides in the concrete.

This article provides information on the chemical characterization of surfaces by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS). It describes the basic theory behind each of these techniques, the types of data produced from each, and some typical applications. The article explains the strengths of AES, XPS, and TOF-SIMS based on data obtained from the surface of a slightly corroded stainless steel sheet.

This article discusses the operating principles, advantages, and limitations of scanning electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, and secondary ion mass spectroscopy that are used to analyze the surface chemistry of plastics.

This article briefly introduces the concepts of failure analysis and root cause analysis (RCA), and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. It reviews four fundamental categories of physical root causes, namely, design deficiencies, material defects, manufacturing/installation defects, and service life anomalies, with examples. The article describes several common charting methods that may be useful in performing an RCA. It also discusses other failure analysis tools, including review of all sources of input and information, people interviews, laboratory investigations, stress analysis, and fracture mechanics analysis. The article concludes with information on the categories of failure and failure prevention.

This article covers the three most popular techniques used to characterize the very outermost layers of solid surfaces: Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectrometry (TOF-SIMS). Some of the more important attributes are listed for preliminary insight into the strengths and limitations of these techniques for chemical characterization of surfaces. The article describes the basic theory behind each of the different techniques, the types of data produced from each, and some typical applications. Also discussed are the different types of samples that can be analyzed and the special sample-handling procedures that must be implemented when preparing to do failure analysis using these surface-sensitive techniques. Data obtained from different material defects are presented for each of the techniques. The examples presented highlight the typical data sets and strengths of each technique.