![]() 27 believed that the existence of Cr element can replace the nano-sized goethite particles to create a denser protective rust layer in the inner rust layer. 26 found that Cr is mainly in the forms of Cr(OH) 3, CrOOH, or FeCr 2O 4 in the rust layer, that is, Cr mainly exists in the form of Cr 3+ among the participants during the iron oxide process. After analyzing the rust layer structure of Cr-containing steel, Jiang et al. Other studies also found that a pseudo-passivation film formed on some Cr-containing steels in the CO 2 corrosion environment, and this film is consisted of Cr(OH) 3 24, 25. A Cr-enriched inner layer mainly consists of α-(Fe 1− x,Cr x)OOH, a Cr substituted FeOOH, which acts as a final stable protective layer. The rust layer of corrosion-resistant steel after long-term exposure to the atmosphere has a two-layer construction, and a significant difference Cr content presents in the inner and outer layers, respectively 23. However, a minimum of 0.10 wt% Cu is required in order to significantly improve the corrosion resistance of the steel 22. Several studies 17, 18, 19, 20, 21 found that Cu can enhance the stability of the rust layer when used together with Cr, thus improving the corrosion resistance of weathering steel. 16 on the atmospheric corrosion behavior of weathering steel in the tropical marine environment found that the weathering resistance of weathering steel is related to the deposition of chloride ions and the enrichment of Cr in the rust layer and that the latter can significantly improve the corrosion resistance of weathering steels in environments with low chloride ion deposition. Several studies have focused on the effect of alloying elements on the corrosion resistance. The recent researches have suggested that addition of Cr, Cu, or P alloying elements can significantly improve the rust layer structure stability of the weathering steel, thereby improving its applicability in severe industrial and marine environments 9, 10, 11, 12, 13, 14, 15. By adding certain amounts of corrosion-resistant elements, a dense rust layer is formed on the steel surface, which can impede further corrosion process of the substrate to achieve improvement of the steel corrosion resistance 4, 5, 6, 7, 8. One of the typical examples is weathering steel. In recent years, a method to improve the corrosion resistance of materials is to form a dense and stable rust layer. ![]() The terms "Standard Reference Material" and the diamond-shaped logo which contains the term "SRM," are registered with the United States Patent and Trademark Office.It is well known that the corrosion resistance of materials can be improved by adding corrosion-resistant alloying elements 1, 2, 3. ![]() ![]() ![]() Note: An SRM is prepared and used for three main purposes: (1) to help develop accurate methods of analysis (2) to calibrate measurement systems used to facilitate exchange of goods, institute quality control, determine performance characteristics, or measure a property at the state-of-the-art limit and (3) to ensure the long-term adequacy and integrity of measurement quality assurance programs. Commercial reference materials producers may affix the NTRM trademark to materials produced according to these criteria and protocols.Ī CRM issued by NIST that also meets additional NIST-specific certification criteria and is issued with a certificate or certificate of analysis that reports the results of its characterizations and provides information regarding the appropriate use(s) of the material (NIST SP 260-136). This traceability linkage is established via criteria and protocols defined by NIST. Certain definitions, adopted for SRM use, are derived from international guides and standards on reference materials and measurements while Other Manufacturers have been developed by the SRM Program to describe those activities unique to NIST operations.Īn NTRM (NIST Traceable Reference Material) is a commercially produced reference material with a well-defined traceability linkage to existing NIST standards. The SRM Program references a number of definitions in connection with the production, certification, and use of its SRMs and RMs. In addition, NIST has published many articles and practice guides that describe the development, analysis and use of SRMs. Each NIST Standard Reference Material® is supplied with a Certificate of Analysis and a Materials Safety Data Sheet, when applicable. ![]()
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