Case Histories

Sampling Drinking Water: Methods and Problems

Water can acquire some aspect of every material it touches. Some of those materials are in such minute quantities, however, that they are virtually undetectable. This article discusses the importance of proper water sampling and analysis when investigating copper and lead concerns.

Pipeline Restoration at a Generating Station Using Chemical Grout

A gravity-flow water inlet line had developed many ruptures and cracks, leading to appreciable groundwater inflow. Contaminants brought in by the groundwater increased the cost of treating the water for station use. The problem was solved by injecting chemical grout to the exterior side of the pipe.

Wireless Remote Monitoring of Cathodic Protection Systems

Wireless monitoring technologies provide the ability to acquire impressed current cathodic protection (ICCP) system performance data from remote locations using modem-equipped personal computers. The technology can monitor the remote ICCP system’s amperage, “instant-on” and “instant-off” potentials in a central location, and provide personnel with immediate warnings of system problems. Case studies are presented for one Air Force and three Army installations, each with a different approach for the monitoring.

Premature Coating Disbonding on Ships and Offshore Structures

Epoxy/urethane coating systems are widely used for ships and offshore structures because of their excellent resistance to ultraviolet radiation and protection against corrosion. Recently, some of these coating systems used in Korea experienced premature failure. This work investigated the root cause of the failures using pH tests and Fourier transform infrared spectroscopy.

Long-Term Performance of a Fluoropolymer- Lined Process Vessel

An ethylene chlorotrifluoro-ethylene (ECTFE) lining of a process vessel handling alkaline-based fluids and active chlorine was examined after more than 23 years of service. The examination and tests showed that the ECTFE material was undamaged. Test procedures, data evaluation, and conclusions are presented.

Caustic Treatment of Electric Utility Drum Boilers

Until recently, caustic water treatment was not used in high-pressure electric utility drum boilers in the United States because of concern over caustic gouging. Meanwhile, it was being used successfully in other countries. Many U.S. electric utilities have now converted their drum boilers to caustic treatment. This article describes the basics of caustic treatment and presents two case histories of successful use in the United States.

Restoration of a Brick Chimney with a Dual Lining System and Polymer Concrete

A brick flue at a generating station was in need of rehabilitation because of the spalling and cracking of the brick. This caused a leakage of acid gases into the annulus. A typical flash coat system was not desired because of its relatively short life. A system of corrosion-resistant materials, which has shown excellent performance and durability, was chosen to make the repairs. The system consists of a combination of organic and ceramic-based lining materials. A case history is presented, with descriptions of the operating environment and materials selection criteria.

Measurement of a Corrosion Inhibitor Through Online Monitoring

Typical repair of reinforced concrete structures showing corrosion damage involves removal of carbonated or chloride-contaminated concrete and subsequent retrofilling with new concrete. Corrosion inhibitors that can be applied by spraying onto the concrete surface are an alternative. These products are relatively new and only limited long-term monitoring results are available. The combination of an inhibitor with monitoring of the corrosion behavior provides evidence of protection. This article describes long-term monitoring results of protected highway gallery columns in the Swiss Alps.

Real-Time Monitoring Affects Cathodic Protection

The need for real-time data is affecting the ability to provide cathodic protection (CP) to pipelines. The connection of electronic equipment required for remote pressure monitoring, metering information, valve operators, and other functions creates a direct short from the CP on the pipeline to the electric power company alternating current grounding system. In essence, the CP system now must protect not only the pipeline, but also a sizeable bare copper grounding grid. This problem creates pipe-to-soil potentials that may not meet the desired criterion. This article covers the use of decoupling devices to remedy this problem.

Copper Pipe Failure by Microbiologically Influenced Corrosion

After a detailed investigation on the failure of copper water service pipes in a water distribution system, microbiologically influenced corrosion (MIC) was found to be the cause. Increased system disinfection appears to have remedied the problem. MIC is often overlooked in corrosion investigations of drinking water systems. This case history is a good example of telltale signs of MIC and the water environments in which this can occur.

Hot Oil Aboveground Storage Tank Bottom Corrosion Failure and Cathodic Protection Upgrade—Part 2

Several types of anode installations for tank bottoms are possible, but the methods selected do not always produce the desired results. This two-part article discusses a case history in which existing cathodic protection (CP) was ineffective and testing methods did not identify system deficiencies. This led to the premature failure of the tank bottom. Part 1 covered the findings of an investigation conducted to identify the cause of the corrosion. Part 2 describes the remedial approach taken to enhance CP for effective corrosion control.

Di-Octyl Sebacic Acid in Epoxy Paint Leads to Blistering in a Drum and Barrel Manufacturing Plant

Di-octyl sebacic acid (DOS-A) is used as rust preventive oil on steel sheets. When applied below the maximum level of 75 mg/m2 per side, it is compatible with epoxy paint and does not require any pretreatment of the steel sheets. The incompatibility of DOS-A above this maximum could be caused by weak H-bonding between the acid and epoxy molecule, leading to blistering. The optimum oil level was determined through experimentation to avoid paint failure. It was also observed that a variance in the sheet surface roughness of ±0.4 µm did not appreciably affect paint failure.

Evaluation of the Scale and Inhibition Effect of a Water Stabilizer

The complex effect of a water stabilizer on copper, iron, and zinc ions was tested by spectrophotometry, and its corrosion inhibition on copper alloy tubes was measured using electrochemical methods. The results showed that the water stabilizer not only had a strong antiscaling effect on Ca2+ and Mg2+, but also had certain complex effects on Cu2+ and Zn2+ under conventionally used concentration. The water stabilizer provided insufficient corrosion inhibition on copper tubes at the usual concentration.

Hot Oil Aboveground Storage Tank Bottom Corrosion Failure and Cathodic Protection Upgrade—Part 1

There are several types of anode installations that distribute protective current to a tank bottom. In some cases, however, the methods selected do not always produce the desired results. This two-part article discusses a case history in which existing cathodic protection (CP) was ineffective and the methods used to verify the performance of CP did not identify system deficiencies. This led to the premature failure of a tank bottom. Part 1 covers the findings of an investigation conducted to identify the cause of the corrosion. Part 2 discusses the remedial approach taken to enhance the CP for effective corrosion control.

Prevention of Micro-Flow Marks in Cathodic Electrodeposited Primer Coating in Automotive Industries

There was a defect of severe micro-flow mark lines in cathodic electrodeposited (CED) primer coating on car components. This problem was highlighted after final painting. This article describes the tests performed to determine the root cause of the defect. Tests included a surface profile of the CED coating and the determination of the microstructure and nickel content of the phosphate coating beneath the CED coating. The investigation identified the optimum concentration of nickel in the coating to refine phosphate grain size and create a unity crystal aspect ratio. It also found that the triple point junction of phosphate crystals determines the porosity to provide a uniform CED coating surface finish.