Corrosion Product Characterization of a Nickel-Sodium Sulfate-Air System after Exposure to Temperatures Near 1000 C

CORROSION ◽  
1974 ◽  
Vol 30 (4) ◽  
pp. 131-138 ◽  
Author(s):  
RICHARD F. REISING ◽  
DOUGLAS P. KRAUSE

Abstract Gas turbine engines are susceptible to high temperature corrosion which is enhanced by marine atmospheres. This high temperature corrosion is also known as sulfidation because it is believed that the formation of metal sulfides from sulfur containing substances is essential. An understanding of the corrosion mechanisms involved is necessary in seeking methods of eliminating the problem, and the initial step in formulating mechanisms is to identify the chemical reactions involved. Corrosion product characterization is essential for this identification. Characterization of the corrosion products from the nickel-sodium sulfate-air system at temperatures near 1000 C (1832 F) suggests that the sodium sulfate acts as a flux rather than as a chemical reactant. Some of the techniques used to characterize the corrosion products are discussed.

2014 ◽  
Vol 28 (10) ◽  
pp. 6447-6458 ◽  
Author(s):  
Sunday Chukwudi Okoro ◽  
Melanie Montgomery ◽  
Flemming Jappe Frandsen ◽  
Karen Pantleon

CORROSION ◽  
10.5006/2802 ◽  
2018 ◽  
Vol 74 (9) ◽  
pp. 984-1000 ◽  
Author(s):  
Esmaeil Sadeghi ◽  
Nicolaie Markocsan ◽  
Tanvir Hussain ◽  
Matti Huhtakangas ◽  
Shrikant Joshi

NiCrMo coatings with and without dispersed SiO2 were deposited using high-velocity air-fuel technique. Thermogravimetric experiments were conducted in 5% O2 + 500 vppm HCl + N2 with and without a KCl deposit at 600°C for up to 168 h. The SiO2-containing coating showed lower weight change as a result of formation of a protective and adherent Cr-rich oxide scale. SiO2 decelerated short-circuit diffusion of Cr3+ through scale’s defects, e.g., vacancies, and promoted the selective oxidation of Cr to form the protective Cr-rich oxide scale. Furthermore, the presence of SiO2 led to less subsurface depletion of Cr in the coating, and accordingly less corrosion of the substrate. The formed corrosion product on the SiO2-free coating was highly porous, non-adherent, and thick.


2013 ◽  
Vol 212 ◽  
pp. 137-140 ◽  
Author(s):  
Janusz Cebulski ◽  
Stanisław Lalik

The aim of this paper was to determine the resistance to high-temperature corrosion in atmosphere of air for alloy Fe-40Al-5Cr-0.2Ti-0.2B. Corrosion tests were conducted in temperatures from 600 to 900°C in time from 2 to 64 hours. Conducted tests have shown a slight increase of weight of samples in periods of time which followed. Increase of weight is connected with corrosion products in the form of passive oxides which form on the surface of the alloy. Kinetics of corrosion processes has parabolic course in tested temperature range which proves the formation of passive layers of corrosion products on the surface of samples. Heat resistance of the alloy on intermetallic phase matrix FeAl brings about potential possibilities to apply this alloy as a material meant for work in elevated and high temperatures in the environment which includes oxygen.


MRS Bulletin ◽  
1994 ◽  
Vol 19 (10) ◽  
pp. 23-25 ◽  
Author(s):  
J.C. Colson ◽  
J.P. Larpin

The first stainless steels, mainly low carbon chromium-iron alloys, have been known since the beginning of this century. These steels show good resistance against wet corrosion and high-temperature corrosion. This article focuses on high-temperature corrosion, with emphasis on gaseous sulfidizing and oxidizing environments. The discussion is limited to these two gases since corrosion involving halogen-and/or carbon-containing gases involves other specific processes. The behavior of binary and ternary alloys will be successively examined, then the role of minor elements will be considered.Fundamental Mechanisms of High-Temperature Corrosion of Stainless SteelUsually, a dry corrosion process results in the formation of corrosion products, giving a simple or complex oxide or sulfide scale on a metallic substrate, separating it from the aggressive gaseous environment and, consequently, acting as a protective barrier. Scale growth is controlled by the conductivity of the reaction products which are solid electrolytes. Generally, the mechanism of scale growth is governed by outward cation or inward anion diffusion processes. This is the basis of the model originally put forward by Wagner for a single metal and subsequently developed for alloys, and particularly, for stainless steels. This one-way point-defect diffusion process is responsible for the observed parabolic scaling kinetics characterized by a parabolic rate constant kp. This model is well described in the literature.In the case of stainless steels, formation of a protective scale is required; this is possible if the oxide or sulfide products have a low diffusivity to cations or anions due to a low density of point defects in the crystal lattice. The protective characteristics of the corrosion products may be experimentally determined by measurement of their electrical conductivity, although the scales should also be effective against short-circuit transport of ions, atoms, or molecules. The best barriers consist of oxides, such as Al2O3, SiO2, and Cr2O3.


2001 ◽  
Vol 43 (10) ◽  
pp. 1891-1903 ◽  
Author(s):  
C.-H Xu ◽  
W Gao ◽  
M Hyland ◽  
H Gong

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