Coal Age

OCT 2018

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36 October 2018 corrosion continued fense against corrosion. A white ceramic layer then forms over the alloy layer. This ceramic layer, the second line of defense, provides a reservoir of phosphate corro- sion protection to continuously maintain the alloy layer. The coating was developed and patented several years ago by North Carolina, USA-based EonCoat LLC. SPI Performance Coating, a U.K. dis- tributor for EonCoat, recently reported that one of world's largest underground mines had used it successfully to extend the life of a troublesome process hopper that han- dles thousands of tons of iron ore material weekly. Natural salts contained within the material, combined with water condensa- tion, created perfect conditions for corro- sion of the hopper's steel components. Before the EonCoat application could begin, heavy deposits that had built up on the hopper walls had to be mechanically chipped away, followed by abrasive blast- ing, and then washing with potable water to remove blasting debris from the metal surface. According to SPI, the level of salt content in the area became highly appar- ent when the hopper's steel began to flash- rust minutes after the washing process. EonCoat CR was applied to the lower section of the steel hopper at a nominal thickness of 800 µm WFT in a single coat, applied over an eight-hour shift. The fol- lowing morning the entire area was pres- sure-washed to allow the applicators to determine if the process had been success- ful. EonCoat simply washes off if it doesn't fully react with the substrate, allowing the applicator to remedy any problems before returning equipment to service, accord- ing to SPI. Over the whole area, only three small patches needed reapplication. SPI reported that, upon inspection, passivation of the steel from formation of magnesium iron phosphate produced no pinholes, voids or delaminations in the fin- ished EonCoat application. This, said the company, is due to the reaction between the acid and base, creating a negative charge within EonCoat CR that physically pulls it into every surface imperfection. Approaching steel-corrosion prob- lems from a different direction, Fluoram- ics, a supplier of engineered Polytetra- fluoroethylene (PTFE)-based corrosion solutions, announced it now offers a way for metal fabricators and welders to pro- tect steel from corrosion without impair- ing their ability to weld it. Fluoramics said its HinderRUST S4.0 rust inhibitor recent- ly passed extensive testing at the Welder Training and Testing Institute (WTTI) in Allentown, Pennsylvania, USA, to assure welders that they can weld steel directly through this HinderRUST formulation. HinderRUST S4.0 is used in the metal fabrication industry to prevent corrosion of steel. Solvent-free S4.0 can be applied to steel parts or plates by brush, roller or aerosol spray can, and it will immediately displace moisture on the treated surface and protect the steel from rust for up to two years. Fluoramics said it was interested in determining if strong, secure welds can be made to steel treated with S4.0, and consequently had WTTI conduct a series of tests on A/SA516 Grade 60/70 steel of a uniform thickness of 0.375 in. The steel pieces treated with HinderRUST S4.0 passed all tests, including two transverse face bends, two transverse root bends, two tensile strength tests, and both visual and radiographic inspections. And, under its Master Builders brand, BASF offers MasterProtect 8020CI, a sur- face-applied corrosion inhibitor that the company said is designed to migrate through even the densest concrete struc- tures and form a layer on the steel reinforc- ing bars. MasterProtect 8020CI also protects other metals including carbon steel, galva- nized steel and aluminum. According to the company, MasterProtect 8020CI will stop the further corrosion of reinforcing metals and extend the service life of the structure. The principal benefits of MasterPro- tect 80201CI, according to BASF, include: • Reduces corrosion rate of corroding steel not yet visible; • Provides protection in new structures where insufficient cover is an issue; • Stops the formation of incipient an- odes at new to old concrete interface; • Does not interfere with bond of re- pair mortars or coatings — can be used directly on areas to be repaired; • Forms passive layer underneath rust on steel — slows corrosion to allow for longer term repair strategy to be put in place; • Easy application; • Water-based; • Allows concrete to breathe and vapor to diffuse — is not a vapor barrier; • Dual action inhibitor — protects both anodic and cathodic areas; and • No cure time required. Protecting Control Equipment To be sure, not all corrosion-preventative solutions focus on the steel and concrete substrates that constitute much of the min- ing industry's asset base. The degradation of electrical control equipment by corro- sive gases and substances is a well-known process and, as air filtration specialist Camfil pointed out, heavy industries such as mining are becoming increasingly reli- ant on electronic and electrical controls for the safe and efficient operation of various -— often automated — processes. In many industrial environments, the external air around a facility may contain acidic gas- es. Plus, fine particles in the atmosphere, containing corrosive contaminants in the form of salts of ammonium and sulfate that retain moisture, may come to rest on control equipment. Either of these condi- tions can lead to corrosion problems. Camfil said molecular filtration using adsorption technology is the industry-ac- cepted method to remove corrosive agents from the air. The company's corrosion control solution includes evaluation of a site's environmental conditions; provid- ing filtration solutions in accordance with corrosive-gas concentration levels and the operating conditions of the existing venti- lation systems; and on-site performance monitoring, in accordance with applicable standards such as ANSI/ISA -71.04-2013 and IEC 60721-3-3. Filter supplier AAF Flanders also fo- cuses on the problem, noting that strict- er environmental guidelines have forced many manufacturers to replace lead-based solders with lead-free solutions, which are more susceptible to corrosion of circuit boards and components from airborne gaseous and particulate contaminants. These forms of corrosion can cause failure by either impeding the flow of electricity or forming unintended circuit paths. In response to these problems, the industry has developed a standard to classify control rooms and process con- trol environments. Most equipment manufacturers require that a control room environment meets the ISA G1— Mild classification to maintain a reliable communication network in industrial environments. The only way to meet this requirement in many industrial environ- ments, according to AAF Flanders, is with adequate gas-phase and particulate filtra- tion in control-room spaces.

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