Selective corrosion, steels

Other methods of metal powder manufacture are also employed for specific metals. Selective corrosion of carbide-rich grain boundaries in stainless steel, a process called intergranular corrosion, also yields a powder. 

There are no films or protective surface films on active metals, e.g., mild steel in acid or saline solutions. Passive metals are protected by dense, less readily soluble surface films (see Section 2.3.1.2). These include, for example, high-alloy Cr steels and NiCr alloys as well as A1 and Ti in neutral solutions. Selective corrosion of alloys is largely a result of local concentration differences of alloying elements which are important for corrosion resistance e.g., Cr [4],... 

Selective corrosion in the heat-affected zone of a weld occurs most commonly when unstabilised stainless steels are used in certain environments. The obvious answer is to use an extra-low-carbon grade of stainless steel, e.g. types 304L, 316L or a stabilised grade of steel, e.g. types 321 and 347. Knifeline attack at the edge of a weld is not commonly encountered and is seldom predictable, and it must be hoped that it is revealed during preliminary corrosion testing. 

In condensed moisture, there is sufficient corrosion of zinc to give protection at pores in a coating on steel without the formation of as much zinc corrosion product as would develop on a wholly zinc surface. In solder-ability the coating is tin-like when new or stored dry, but the selective corrosion of zinc in humid conditions may produce a layer obstructive to easy soldering. 

The selective corrosion of cast iron (graphitization), the preferential corrosion of the steel welding (grooving corrosion), sensitization and knife line attack of welded stainless steels are typical examples of corrosion influenced by metallurgical parameters. 

Secondly, we focused on the role of oxygen impurities in element-selective corrosion of austenitic stainless steels in liquid sodium. Calculation was carried out for an oxygen impurity associated with an Na atom located at the site on top of a Cr atom at the Fe(OOl) surface in sodium. The result shows that a positively charged Cr atom will be released selectively into sodium by an 0 anion. 

Mechanism of the element-selective corrosion of austenitic stainless steels... 

Secondly, we examined the mechanism of element-selective corrosion of austenitic stainless steels in liquid sodium. We performed calculations for a system where an 0 impurity atom accompanying Na atom approaches Or atom at an Fe(OOl) surface exposed to liquid sodium. The energy levels attributed to the Cr 3d orbitals are located above the Fermi level, while the energy levels originated from the 0 2p orbitals are below the Fermi level. Furthermore, the level for the Na 3s orbital is above the Fermi level. By the energy differences of these orbitals, the Cr atom is charged positively, while an 0 atom accompa-... 

In selecting the steel wool, two criteria have to be fulfilled (i) it should be corrosion resistant to not interfere with the iron determination of the ML preparations, and (ii) it should be highly magnetisable which is not evident for common stainless steel materials. 

Table 2.27. Guide for selected stainless steels (corrosion, oxidation, fabrication, application) ...

M.F. Hurley and J.R. Scully, Threshold chloride concentrations for localized corrosion on selected corrosion resistant rehar materials compared to carbon steel. Corrosion Journal 62(10) 892-904, 2006. 

Brush, E. G., "Sodium Mass Transfer XVI. The Selective Corrosion Component of Steel Exposed to Flowing Sodium, Atomic Energy Commission Research Development Program, General Electric Corp. GEAP-4832, March 1965. 

Gerhold, W. F., Escalante, E., and Sanderson, B. T., "The Corrosion Behavior of Selected Stainless Steels in Soil Environments, NBSIR 81-2228(NBS), American Iron and Steel Institute, Washington, DC, February 1981. 

Selektive Korrosion an VerbindungsschweiKen von Stahlen (Selective corrosion on joint-welding of steels) (in German)... 

Cobum S. Atmospheric corrosion. In Korb, LJ. Metals Handbook, 9th ed, Vol. 1, Properties and Selection, Carbon Steels. Metals Park, Ohio American Society for Metals, 1978 720. 

Chromium concentration near the grain borders can be as low as 8 -10 wt%, that is, below the limit that ensures the corrosion resistance of steel [22], The presence of an electrolyte, in our case fused chloride mixture, leads to the formation of microgalvanic elements and selective corrosion of zones depleted in chromium. For this reason the IGC is spread only along the zones adjoining boundaries of grains depleted in chromium. 

Archer ED, Brook R, Edyvean RGJ, Videla HA (2001) Selection of Steels for use in SRB Environments, Paper No. 01261, Corrosion 2001, NACE International Sanchez del Junco A, Moreno DA, Ranninger C, Qrtega-Calvo JJ, Saiz-Jimenez C (1992) Microbial induced corrosion of metallic antiquities and works of art A critical review. International Biodeterioration Biodegradation (29) 367-375... 

Chaves R, Costa 1, de Melo HO, Wolynec S (2006) Evaluation of selective corrosion in UNS S31803 duplex stainless steel with electrochemical impedance spectroscopy. Electro-chimica Acta (51) 1842-1846... 

Archer ED, Brook R, Edyvean RG, Videla HA (2001) Selection of steels for use in SRB environments. Paper No. 01261. CORROSION 2001, NACE International Javaherdashti R, Raman Singh RK, Panter C, Pereloma EV (2004) Stress corrosion cracking of duplex stainless steel in mixed marine cultures containing sulphate reducing bacteria. Proceedings of Corrosion and Prevention 2004 (CAP04), 21-24 November 2004, Perth, AustraUa... 

Corrosion resistant steels commonly used for plastics processing are 1.2082,1.2083, and 1.2316. The requirements decide in detail which steel should be chosen since in addition to the above described factors, other criteria must be considered in the selection of steel. The following criteria are examples for this ... 

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