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.
Several factors cause deterioration of critical process
equipment in process plants. The options widely
utilized for restoration include conventional repair
or replacement. Nonmetallic composite materials
can be utilized as an option to restore equipment
integrity. This article discusses the material
degradation aspects in critical streams such as the
cooling water system and hydrocarbon pipelines at a
Saudi Arabian gas plant. Nonmetallic composite
coating materials play a vital role in corrosion
protection and life extension of core components.
Components of water treatment plants (WTPs) are
susceptible to corrosion from constant immersion in water
and proximity to chlorine. A case history of corrosion
problems and their treatment at an Army WTP is
presented. Solutions included using high micro-silica
restoration mortar and advanced coal tar epoxy coatings.
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.
This article outlines the results of a long-term
pipeline integrity plan that was used to rehabilitate
large segments of a natural gas pipeline over the past
eight years. Part 1 of this article discussed the details to be followed in an effective rehabilitation plan to accomplish the goal of a well-maintained pipeline system.
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.
Carbonated amine material, often called amine
blush, is the reaction product of the amine
functional curatives in epoxy paint with carbon
dioxide (CO2) and water vapor. This article explains the formation of amine blush and discusses factors controlled by the applicator and those controlled by the paint manufacturer.
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.
Faced with serious concrete deterioration from
biogenic sulfide corrosion within collection systems,
engineers and municipalities are extending the
service life of wastewater conveyance structures with
the use of 100% solids polyamine systems designed
for hydrogen sulfide (H2S) permeation resistance. This article explains how sewer interceptors, manholes, and lift stations were protected using fluid-applied linings.
A chlorine scrubber fabricated from fiberglass-reinforced plastic (FRP) was installed in 1977.
Major repairs began in 1981 and continued at
four-year intervals. After exploring several
replacement materials, a FRP/ethylene-chlorotrifluoroethylene dual laminate scrubber was selected. This was installed in 1987 and remained in continuous service until the plant shut down in 2001. Examination shortly after plant closing showed the liner to be in excellent condition.
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 purpose of this article is to draw some attention to the importance of surface preparation and coating inspection and perhaps change some attitudes and the all-too-common practice of assigning less than qualified and experienced personnel to inspect surface preparation and coatings.
The “Spoonbridge and Cherry” is an iconic sculpture in Minneapolis, Minnesota. Recently, concern was expressed over the condition of the cherry and its coatings. The cherry was inspected, removed, and recoated. This article describes the rehabilitation process and the materials used.
Organic coatings include latex paints, plastics, asphaltic materials, rubbers, and elastomers. The specific material selected for a coating job must have characteristics that would allow its proper application under all conditions existing during the coating process. Proper identification of the physical or other properties of the film expected from the application must be specified.
Proper surface preparation is an essential preliminary step for any coating application. It is false economy to skimp on surface preparation in the belief that the coatings applied will compensate for surface deficiencies. This is especially true of high-performance coating materials.