Tantalum as a material of construction for the chemical processing industry – A critical survey

Abstract

Dedicated to Professor Dr. Elsbeth Wendler-Kalsch on the occasion of her 60th birthdayMaterials selection is based on safety and economic considerations; the least expensive material securely withstanding service conditions for a required service time is chosen. For the integrity of equipment in the CPI chemical resistance is an essential factor. Of all metallic materials used for CPI equipment, tantalum is second to none regarding chemical inertness, comparing only to resistance properties of the nonmetals glass, fluoropolymers, and graphite. The price of tantalum, however, prohibits its broad application for construction. There are only two ways by which the demand for tantalum in this field can be promoted significantly. First, a major increase in the aggressivity of service conditions in process engineering caused by process development or modification. Second, cost reduction via tantalum price dilution by means of duplex systems application, utilizing the advantages of a less expensive base metal and a thin tantalum lining or coating. The more important systems of this type are discussed and evaluated regarding their potential of development.Die Werkstoffauswahl orientiert sich an Sicherheits-und Wirtschaftlichkeitsvorgaben. In der Regel wird die preiswerteste Losung gewahlt, mit der ein ungestorter Betrieb wahrend der vorgesehenen Betriebsdauer gewahrleistet ist. Fur den Chemieanlagenbau spielt die chemische Resistenz von Werkstoffen eine entscheidende Rolle. Hinsichtlich der Korrosionsbestandigkeit liegt Tantal dabei an erster Stelle der metallischen Werkstoffe; es wird daher verglichen mit den Nichtmetallen Glas, Fluorpolymere und Graphit. Ein umfangreicherer Einsatz von (monolithischem) Tantal verbietet sich allerdings aufgrund seines Preises. Eine signifikante Zunahme der Anwendung w&re lediglich unter zwei Bedingungen zu erwarten: Zum einen wiirde eine deutliche Verscharfung der chemischen Prozeljbedingungen zur Spezifizierung von Werkstoffen hoherer Bestandigkeit zwingen. Zum anderen konnten durch Wahl von Verbundsystemen mit Tantal als produktseitigem Material die hohen spezifischen Kosten dieses Metalls reduziert werden. In der vorliegenden Arbeit werden die verschiedenen Moglichkeiten derartiger Verbundsysteme erortert und qualitativ bewertet.

Tantalum oxide thin films as protective coatings for sensors

“…Besides, tantalum is used in chemical processing equipment because it is extremely stable. The reason for this is the formation of a thin amorphous tantalum oxide layer at the surface, which is chemically very inert [8]. Deposition of tantalum and its oxides and nitrides can be done by physical vapour deposition, by chemical vapour deposition, or by thermal oxidation.…”

Continuous Flow Synthesis of n-Alkyl Chlorides in a High-Temperature Microreactor Environment

“…Owing to the corrosiveness of HCl, process intensification using high-temperature/high-pressure conditions is a nontrivial affair, using either batch or continuous flow processing. The most common choice for processing highly corrosive concentrated HCl at elevated temperatures in industry are high performance Ni-based (Hastelloy C-276, Hastelloy B-3), or Ta-based alloys (Ta, Ultra 76), in addition to certain types of ceramic materials (for example SiC) . Since the chemical resistance of these materials toward aqueous concentrated HCl in an elevated temperature and pressure regime has not been fully documented, − and in addition since these materials are exceedingly expensive and difficult to manufacture, we have opted to use standard glass microreactors for our laboratory-scale investigations (see below).…”

Growth Mechanisms of TaN Thin Films Produced by DC Magnetron Sputtering on 304 Steel Substrates and Their Influence on the Corrosion Resistance

“…In previous investigations, it has been constantly reported that physical vapor deposited (PVD) coatings are characterized by possessing different types of defects such as holes, cracks, and impurities, among others, due to their chemical composition, structure, and deposition parameters. In aggressive environments, these defects can be direct paths to the substrate, thus causing localized corrosion and a decrease in protective efficiency [55]. The energy with which the material strikes the growing film during its deposition can also influence the density of these defects through the variation of the energy with which the ions reach the surface of the substrate, which could influence the atomic distribution surface and generate changes in the corrosive behavior of coatings.…”