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Galvanization or galvanizing is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are submerged in a bath of hot, molten zinc.
Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)3), and is typically associated with the corrosion of refined iron.
Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials by chemical or electrochemical reaction with their environment. Corrosion engineering is the field dedicated to controlling and preventing corrosion.
Passivation, in physical chemistry and engineering, refers to coating a material so it becomes "passive", that is, less readily affected or corroded by the environment. Passivation involves creation of an outer layer of shield material that is applied as a microcoating, created by chemical reaction with the base material, or allowed to build by spontaneous oxidation in the air. As a technique, passivation is the use of a light coat of a protective material, such as metal oxide, to create a shield against corrosion. Passivation of silicon is used during fabrication of microelectronic devices. In electrochemical treatment of water, passivation reduces the effectiveness of the treatment by increasing the circuit resistance, and active measures are typically used to overcome this effect, the most common being polarity reversal, which results in limited rejection of the fouling layer.
A galvanic anode, or sacrificial anode, is the main component of a galvanic cathodic protection system used to protect buried or submerged metal structures from corrosion.
Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. A simple method of protection connects the metal to be protected to a more easily corroded "sacrificial metal" to act as the anode. The sacrificial metal then corrodes instead of the protected metal. For structures such as long pipelines, where passive galvanic cathodic protection is not adequate, an external DC electrical power source is used to provide sufficient current.
Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal.
In metallurgy, a flux is a chemical cleaning agent, flowing agent, or purifying agent. Fluxes may have more than one function at a time. They are used in both extractive metallurgy and metal joining.
A washer is a thin plate with a hole that is normally used to distribute the load of a threaded fastener, such as a bolt or nut. Other uses are as a spacer, spring, wear pad, preload indicating device, locking device, and to reduce vibration.
In chemistry, a corrosion inhibitor or anti-corrosive is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy, that comes into contact with the fluid. The effectiveness of a corrosion inhibitor depends on fluid composition, quantity of water, and flow regime. Corrosion inhibitors are common in industry, and also found in over-the-counter products, typically in spray form in combination with a lubricant and sometimes a penetrating oil. They may be added to water to prevent leaching of lead or copper from pipes.
Aluminium bronze is a type of bronze in which aluminium is the main alloying metal added to copper, in contrast to standard bronze or brass. A variety of aluminium bronzes of differing compositions have found industrial use, with most ranging from 5% to 11% aluminium by weight, the remaining mass being copper; other alloying agents such as iron, nickel, manganese, and silicon are also sometimes added to aluminium bronzes.
A metal roof is a roofing system featuring metal pieces or tiles exibiting corrosion resistance, impermeability to water, and long life. It is a component of the building envelope. The metal pieces may be a covering on a structural, non-waterproof roof, or they could be self-supporting sheets.
The salt spray test is a standardized and popular corrosion test method, used to check corrosion resistance of materials and surface coatings. Usually, the materials to be tested are metallic and finished with a surface coating which is intended to provide a degree of corrosion protection to the underlying metal.
Aluminized steel is steel that has been plated with aluminium or aluminium-silicon alloy, in a process analogous to hot-dip galvanizing. The steel workpiece is immersed in molten aluminum to produce a tight metallic bond between the steel and coating. The product has a unique combination of properties possessed by neither steel alone nor aluminium alone. Aluminized steel is more resistant to corrosion than bare steel while retaining properties of steel, at temperature lower than the melting point of aluminum, 800 °C (1,470 °F). Common applications include heat exchangers in residential furnaces, commercial rooftop HVAC units, automotive mufflers, ovens, kitchen ranges, water heaters, fireplaces, barbecue burners, and baking pans. Aluminized steel transfers heat more effectively than bare steel. It often serves where galvanized steel might have been used historically, without galvanized steel's drawbacks.
Metals used for architectural purposes include lead, for water pipes, roofing, and windows; tin, formed into tinplate; zinc, copper and aluminium, in a range of applications including roofing and decoration; and iron, which has structural and other uses in the form of cast iron or wrought iron, or made into steel. Metal alloys used in building include bronze ; brass ; monel metal and nickel silver, mainly consisting of nickel and copper; and stainless steel, with important components of nickel and chromium.
Corrosion engineering is an engineering specialty that applies scientific, technical, engineering skills, and knowledge of natural laws and physical resources to design and implement materials, structures, devices, systems, and procedures to manage corrosion. From a holistic perspective, corrosion is the phenomenon of metals returning to the state they are found in nature. The driving force that causes metals to corrode is a consequence of their temporary existence in metallic form. To produce metals starting from naturally occurring minerals and ores, it is necessary to provide a certain amount of energy, e.g. Iron ore in a blast furnace. It is therefore thermodynamically inevitable that these metals when exposed to various environments would revert to their state found in nature. Corrosion and corrosion engineering thus involves a study of chemical kinetics, thermodynamics, electrochemistry and materials science.
Copper alloys are important netting materials in aquaculture. Various other materials including nylon, polyester, polypropylene, polyethylene, plastic-coated welded wire, rubber, patented twine products, and galvanized steel are also used for netting in aquaculture fish enclosures around the world. All of these materials are selected for a variety of reasons, including design feasibility, material strength, cost, and corrosion resistance.
According to EN 13523-0, a prepainted metal is a ‘metal on which a coating material has been applied by coil coating’. When applied onto the metallic substrate, the coating material forms a film possessing protective, decorative and/or other specific properties.
Galvanic corrosion is an electrochemical process in which one metal corrodes preferentially when it is in electrical contact with another, in the presence of an electrolyte. A similar galvanic reaction is exploited in primary cells to generate a useful electrical voltage to power portable devices. This phenomenon is named after Italian physician Luigi Galvani (1737-1798).
Flowers of sulfur (FOS) testing was developed to determine the porosity of metallic coatings susceptible to sulfur induced corrosion [see below ASTM B809-95(2018)]. Applicable substrates are silver, copper, copper alloys and any other metal or metal alloy with which sulfur will react. For porosity testing, coatings can be single or multiple layers of any metal that is not corroded and sealed by a self-limiting reaction in the reducing sulfur environment of the FOS test. The simplest recommended technique is to identify any porosity of the coating as revealed by the presence of surface spots. These surface spots form where the environmental sulfur has penetrated and reacted with the base metal, producing a metal sulfide. Chalcocite, copper (I) sulfide is dark-grey to black. Silver (I) sulfide is also grey-black.
References
- ↑ "Marinisation". www.marinepanservice.com. Retrieved 2022-12-05.
- ↑ Petersen, E. L. (2014-01-02). 1999 European Wind Energy Conference: Wind Energy for the Next Millennium. Routledge. p. 289. ISBN 978-1-134-27358-4.
- ↑ IQ, Oil & Gas (2011-08-31). "Corrosion: The Deep And Ultra-Deepwater Problem". Oil & Gas IQ. Retrieved 2022-12-05.
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