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.
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 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.
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.
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.
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.
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.
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.
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.
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.
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 (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.
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.
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.
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.