Masaaki Naka

High Corrosion Resistance of Chromium-Bearing Amorphous Iron Alloys in Neutral and Acidic Solutions Containing Chloride

Abstract The corrosion resistance of amorphous iron alloys, whose practical application is expected because of their outstanding mechanical properties, has been studied by total immersion tests and...

Effect of metalloidal elements on corrosion resistance of amorphous iron-chromium alloys

Abstract Corrosion and electrochemical behaviours of amorphous iron-chromium alloys containing different sets of glass-forming metalloidal elements, boron, carbon, silicon and phosphorus, have been investigated. The corrosion resistance in 0.1N H2SO4 increases in the order of alloys containing silicon, boron, carbon and phosphorus, and the corrosion resistance in 3% NaCl increases in the order of alloys containing boron, silicon or carbon, and phosphorus. Difference in the corrosion resistance of amorphous alloys containing various metalloids has been interpreted in terms of the difference in the formation rate of the chromium-enriched protective film on the surface of alloys.

Corrosion behavior of amorphous and crystalline Cu50Ti50 and Cu50Zr50 alloys

Abstract Corrosion rates and anodic polarization curves of amorphous and crystallinecu 50 Ti 50 and Cu 50 Zr 50 alloys have been examined in various acidic, neutral and alkaline solutions. The amorphous alloys are very stable in acidic and alkaline solutions, but unstable in agressive chloride solutions. The corrosion resistance of these amorphous alloys is higher than that of the crystallized alloys. The high corrosion resistance of amorphous alloys is attributable to the high chemical homogeneity of amorphous alloys without localized crystalline defects such as precipitates, segregates, grain boundaries, etc. Metalloid elements play an important role in the corrosion behavior of amorphous alloys; the addition of phosphorus to amorphous CuTi alloy greatly increases the corrosion resistance, even in 1N HCl.

High corrosion resistance of amorphous FeMo and FeW alloys in HCl

The corrosion rates and electrochemical behaviors of amorphous FexMo13P7C and FexW13P7C alloys have been examined in 1 N HCl, in comparison with corrosion behaviors of amorphous FexCr13P7C alloys. The chromium, molybdenum and tungsten increase significantly the corrosion resistance of amorphous FePC alloys. Amorphous FeCr, FeMo and FeW alloys are immune to pitting corrosion in 1 N HCl. The corrosion resistance of amorphous iron alloys containing Cr, Mo or W of 5 at% or more increases in the order of FeW, FeMo and FeCr alloys.

Change in corrosion behavior of amorphous FePC alloys by alloying with various metallic elements

Abstract Comprehensive work to examine the effect of metallic alloying elements M on the corrosion behavior of amorphous FeM13 P7 C alloys was performed. All alloying elements except manganese are effective in increasing the corrosion resistance of amorphous alloys in various acidic and neutral solutions, regardless of anionic species, pH and oxidizability. The addition of elements more active than iron to amorphous FePC alloy decrease the corrosion rate in an active region during immersion tests, depending upon the passivation capabilities of the alloying elements themselves. When elements nobler than iron are added, the nobler is the alloying element, the higher is the corrosion resistance of amorphous FeM13 P7 C alloys.

Corrosion-resistant amorphous FeC alloys containing chromium and/or molybdenum

Abstract An attempt was made to improve corrosion resistance of amorphous iron-base alloys, which contain only carbon as a metalloid element, by the addition of chromium and/or molybdenum. The addition of both metallic elements is effective in decreasing the corrosion rate. Especially, the addition of certain amounts of chromium leads to spontaneous passivation even in 1 N HCl. The corrosion resistance of amorphous FeCrC alloys is intermediate between those of amorphous FeCrPC and FeCrB alloys. The all-amorphous alloys examined are characterized by immunity to pitting corrosion, even by anodic polarization in 1 N HCl.

Effect of addition of chromium and molybdenum on the corrosion behavior of amorphous Fe-20B, Co-20B and Ni-20B alloys

Abstract A comparison of the corrosion behavior of three series of amorphous boron-bearing alloys in 1 N HCl has been performed as a function of the content of chromium and molybdenum. The addition of up to 20 at.% of chromium to the alloys does not effectively increase the corrosion resistance. Within this range of chromium content, the corrosion resistance is mainly determined by the anodic stability of the alloy: the more noble the alloy, the lower the corrosion rate. The addition of 30 at.% or more chromium and the combined addition of chromium and a small amount of molybdenum to iron- and cobalt-base alloys leads to a sharp decrease in the corrosion rate, while the addition of large amounts of chromium and molybdenum is necesary to increase the corrosion resistance of nickel-base alloys. Because the beneficial effects of chromium and molybdenum appear after they react with the environment, the more active the alloy, the more effective the addition of these elements.