A building, partially clad in fluoropolymer coated aluminum panels, was observed to have an aesthetically unacceptable appearance while still under construction. Once installed on the building, many of the panels exhibited a vertical streaked appearance under certain conditions. When the panels were at ground level, or when the sun was bright, the streaky appearance was not noticeable. However, in conditions of low light, such as during early morning, dusk, or on cloudy days the streaky appearance was reported to become apparent. A visual mock-up, consisting of multiple coated panels that had been approved by the architect as a guide to the anticipated appearance were also present on-site as a reference. This visual mock-up was used as a reference for acceptable appearance of the coated panels.
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In recent decade, the applications of DSS have significantly increased in oil & gas industry, due to their attractive properties compared to austenitic grades with similar corrosion resistance. The DSS products exhibit a better resistance to pitting, stress corrosion cracking and higher mechanical properties compared to other austenitic stainless steel grades. The microstructure of these materials consists of approximately 50% austenite (γ) and 50% ferrite (α) phases, obtained by means of a solution heat treatment.
Oil and gas wells are highly corrosive environments because they contain H2S and CO2. The 13Cr martensitic stainless steel is widely used in the oil and gas industry because of high good corrosion resistance in CO2 gas wells. Generally, the addition of Mo increases the passivity of steel. However, the role of Mo in passive films has not been completely clarified.
Sulfur and acidic impurities in crude oils pose serious hot oil corrosion problems in crude distillation units (CDU) and associated vacuum distillation units (VDU), especially with the increase in processing of lowquality, opportunity crudes.1-4 In the range of 200-400˚C, reactive sulfur compounds cause sulfidation corrosion of ferritic carbon and chrome steels in CDU, VDU, and front ends of downstream units operating at hot oil temperatures.5-7 Over the same temperature range, naturally occurring carboxylic acids in crudes can be so aggressive that higher alloy, austenitic stainless steels containing >2.5% Mo are required for processing high acid oils.8-11 Although sulfidation and acid corrosion occur over the same temperature range, they differ in two significant ways. Sulfidation forms an iron sulfide solid that is semiresistant to further corrosion and relatively insensitive to flow velocity. Acids form oil soluble organic salts that can be washed away especially in areas of high turbulence.12-14
Environmental assisted fatigue, also known as corrosion fatigue, is a well-known degradation phenomenon in structural materials that may develop as a consequence of long-time exposure of components to cyclic loads at the presence of an aggressive environment. This phenomenon constitutes an increased environmental risk for fatigue initiation in many industrial applications. One such application is the piping system in a nuclear power plant where the structural material is subjected to an aggressive water environment. Here, the cyclic loads arise from thermal fluctuations and mechanically induced vibrations.
An innovative thermoplastic type of coating material based on pure isobutene homopolymer was investigated to determine whether it would be fit for purpose in CUI services at low and moderate temperatures up to 120 °C. This polymer is commonly called Polyisobutene (PIB) and has a unique set of properties that are beneficial for protecting metallic structures from corrosion. Polyisobutene is a polyolefin with a chemical structure similar to Polyethylene (PE) and Polypropylene (PP). One of the major differences is that PE and PP are solid materials with a high degree of crystallinity, whereas PIB does not have a crystallization or melting temperature. PIB has a glass transition temperature (Tg) below – 60 °C which indicates that the polymer is a liquid above this temperature.
Coatings for metal protection is a very broad area of research and no single formulation technique is used. Generally, coatings contain micropores, areas of low cross-link density or high pigment volume concentration that provides a diffusion path for corrosive species such as water, oxygen and chloride ions to the coating/metal interface. Therefore, incorporating corrosion inhibitors into a coating system is a basic step required for corrosion protection [1]. Direct addition of corrosion inhibitors has almost always resulted in undesirable leaching of inhibiting molecules and subsequent reactions with the coating matrix. This reduces the effect and duration required to protect the substrate in the aggressive environment. The encapsulation of corrosion inhibitors into a host material as using nanocontainers is an effective delivery system of the corrosion inhibitor in active corrosion protection application [2].
Galvanized protective coatings have been used for structural steel to mitigate steel corrosion in atmospheric exposures and chloride-rich marine environments. The galvanizing process involves dipping steel elements free of surface mill scale in a molten zinc bath where the diffusion of zinc into the steel matrix allows for zinc-iron alloy layers of decreasing zinc concentrations by depth to form in the steel. Oher elements such as tin, antimony and aluminum may be added to the galvanizing bath to control reaction rates, surface appearance and corrosion behavior. Hot-dipped galvanizing provides corrosion protection by developing a barrier layer and in certain conditions provide beneficial galvanic coupling of the zinc-rich layers to the steel.
Impressed current rectifiers are the backbone of a pipeline operator’s cathodic protection (CP) systems. A rectifier’s ability to protect a large length of electrically continuous pipeline considerably improves efficiencies and reduces material costs as compared to galvanic systems. However, like galvanic anodes, impressed current anodes are a consumable asset, and require replacement at the end of their service life to ensure that the rectifier can continue to adequately protect the pipeline.
Corrosion of reinforcing steel is the most significant cause of deterioration of reinforced concrete structures. Exposure to de-icing salts, seawater and chloride-containing set accelerators can play a significant role in reinforcing steel corrosion. Long-term exposure to carbon dioxide is also cited as a contributor to the corrosion of steel in concrete as well.
Asbestos containing textured coatings and other various asbestos containing components are not often thought of as being used on bridges. However, their use on bridges, especially concrete bridges is widespread in some regions and because of this, specific regulatory compliance is required. Knowing how to comply and how proper abatement is performed will keep the contractors and facility owners in compliance, avoid associated liabilities, provide proper employee safety and keep bridge maintenance projects on schedule.
The potential for structural alloys to undergo environmentally assisted cracking in molten salts is relatively unexplored due to their limited industrial application. However, fluoride salts are of prime interest to many advanced reactors including the Kairos Power FHR reactors. Table I summarizes literature studies of EAC in molten fluoride salts. For the ten studies shown, seven are for Ni-Mo-Cr family of alloys (INOR-8 / Hastelloy N or variants) that were used in the Molten Salt Reactor Experiment (MSRE), two studies investigate austenitic stainless steels, and there is one report of EAC in oxygen free high conductivity (OFHC) copper.