Oxidation After Breakdown of the Chromium-Rich Scale on Stainless Steels at High Temperature: Internal Oxidation

Abstract

Breakaway oxidation of alloy 304L at 600°C was studied in four environments (O 2

Experimental and thermodynamic investigations on the chlorine-induced corrosion of HVOF thermal sprayed NiAl coatings and 304 stainless steels at 700 °C

“…The Corrosion of the FeCr(Ni) alloys has been extensively studied in different environments over a temperature range of 500-900°C [47,[59][60][61][62][63][64][65][66][67][68]. It is generally known that the oxide scale typically consists of an outward growing Fe-rich layer and an inward growing layer consisting of spinel oxide; while the original metal/oxide interface separated the two layers.…”

“…Jonsson et al [47,65] to interpret the formation mechanism of the oxide scale on FeCr(Ni) alloys. Fig.…”

“…6(A), two distinctive types of oxide microstructures were observed being separated by a thin Cr-rich and Mn-rich layer, which is possibly the original metal/oxide interface. Kinetic factors also need to be considered that the observed elemental distributions in the scale were determined by the different diffusivities of cations [47,65]. The diagram of the cation diffusion co-efficient in spinel as a dependency of pO 2 at high temperatures shows that Cr 3+ ions diffuse several orders of magnitude slower than Fe 2+ and O 2− in the spinel [69,70], resulting in the formation of outward growing Ferich oxide and inward growing Cr-rich oxide, which agrees well with the experimental observations.…”

Microstructural Study of the Influence of KCl and HCl on Preformed Corrosion Product Layers on Stainless Steel

“…1. This type of morphology is expected to be the result of the fully oxidized regions of previously formed reaction zones [20]. Some pores are observed at the lower part of the Fe 2 O 3 , i.e., the former metal surface, as well as the metal/oxide interface.…”

“…K 2 CO 3 (s). The pre-oxidation parameters were selected based on earlier work [6,15,20] to achieve Fe-rich oxide. The mechanism for breakaway oxidation in the presence of K 2 CO 3 has previously been proposed to be caused by chromate formation on the sample surface [15].…”