On the kinetics of oxidation of austenitic stainless steels AISI 304 and incoloy 800H

The interaction of oxygen with clean surfaces of stainless steels has been studied by spectroscopic ellipsometry and AES. The reaction involves chemisorption and dissolution of oxygen into the surface of the metal via a place-exchange mechanism. Oxide thickening occurs via cation and anion migration under the influence of an electric field. The activation energy increases with increasing oxide thickness and the final activation energy equals the energy needed to break the bonds between oxygen and metal ions in the oxide, suggesting diffusion via lattice sites

On the influence of cold work on the oxidation behavior of some austenitic stainless steels: High temperature oxidation

AISI 304, 314, 321, and Incoloy 800H have been subjected to several pretreatments: polishing, milling, grinding, and cold drawing. In the temperature range 800–1400 K, cold work improves the oxidation resistance of AISI 304 and 321 slightly, but has a relatively small negative effect on the oxidation resistance of AISI 314 and Incoloy 800H. Milling results in an enlargement of the surface area with a factor 2.5

On the oxide formation on stainless steels AISI 304 and incoloy 800H investigated with XPS

The influence of cold work on the initially formed oxide layer on the stainless steels AISI 304 and Incology 800H has been studied by XPS. Oxidations were performed at pressures of 10-6-10-4 Pa and temperatures of 300–800 K. All samples showed a similar oxidation behaviour. The oxidation rates of iron and chromium are of the same order of magnitude at temperatures below 650 K. Subsequent oxidation results in an iron oxide on top of a chromium oxide layer. At temperatures above 650 K the metal surface becomes enriched in chromium, which is preferentially oxidized at these temperatures and pressures. Even prolonged oxidation does not result in an iron-rich oxide surface. Nickel has never been found in its oxidized form. The binding energy of oxygen, in the various oxide layers, is independent of the extent of oxidation and is 530.6 eV

On the influence of cold work on the oxidation of some stainless steels

Oxidation experiments, performed by means of light interference microscopy, give information of the initial oxidation on a microscopic scale. A thin oxide layer on the substrate gives rise to an interference colour, which is directly correlated to the thickness of this layer. It is shown that not all stainless steels react in the same way to the same pretreatments. The oxidation behaviour of drawn AlSI 304 and AlSI 321 is completely different from that of Incoloy 800 H, while the undeformed and recrystallized samples all show the same oxidation behaviour. It is suggested that this behaviour of AlSI 304 and AlSI 321, is caused by the formation of martensite in the deformed austenitic matrix

Esca Studies of Cr-Co Alloys

ESCA examination of films formed on Cr-Co alloys after immersion in 0.1 M NaCl for 24 h has shown that the thickness of passive films decreased with an increase in chromium content. Surface films consisted of chromium and cobalt oxides as Cr2O3 and CoO. The amount of CoO in the surface film of the alloy was decreased with an increase in chromium but Cr2O3 was found at a greater depth in the passive film at any composition. Cr2O3 was a major component of the surface film when the chromium content in the alloy was 10% or higher. Electrochemical techniques according to ASTM G59 and ASTM G5 were used for the determination of the relative corrosion rate. Both Co-10 wt.% Cr and Co-30 wt.% Cr alloys investigated showed a lower corrosion rate than the Co-5 wt.% Cr alloy. Corrosion rate measured could be correlated to the surface film composition and structure as determined by ESCA

Esca Studies of Ni-Cr Alloys

ESCA examination on Ni-Cr alloys has shown that a thin passive film was formed after 24 h immersion in 0.1 M NaCl. The film contained only chromium oxide in the form of Cr2O3. Electrochemical techniques according to ASTM G59 and ASTM G5 were used for the determination of the relative corrosion rate of the alloys. Both Ni-10 wt. % Cr and Ni-20 wt. % Cr alloys showed a slightly higher corrosion rate than the Ni-40 wt. % Cr alloy

Passive Films On Stainless-Steels in Aqueous-Media

The purpose of this paper is to provide a syntheses of experimental results regarding films formed on the surface of stainless steels. Such syntheses are attempted for the environments most studied. In each case the overview is presented with reference to the most important papers. Conflicting data are also presented and discussed. Based on the results of the prior studies, a four region model is proposed to describe the surface passive film and its breakdown