Aluminizing and Corrosion of Carbon Steels in N₂/0.5%H₂S Gas at 650-850℃

Abstract

AbstractsThe effect of hot-dip aluminizing on the corrosion of the low carbon steel was studied at 650-850 o C for 20-50 h in N 2 /0.5% H 2 S gas. The aluminized steel consisted primarily of the Al topcoat and the underlying Al-Fe alloy layer. Aluminizing drastically improved the corrosion resistance by forming the α-Al 2 O 3 surface scale. Without aluminizing, the steel formed nonadherent, fragile, thick scales, which consisted of FeS as the major phase and iron oxides such as FeO, Fe 3 O 4 and Fe 2 O 3 as minor ones.

Microstructural Changes of Al Hot-Dipped P91 Steel during High-Temperature Oxidation

“…Hence, the high-temperature oxidation resistance of 9Cr-1Mo steels needs to be improved through surface modification techniques. Aluminum hot-dipping is a simple, cost-effective coating technique that could form the compact, slow growing, protective alumina scale in reaction with oxygen at high temperatures [4][5][6][7][8][9][10][11][12][13][14][15]. It also improves the surface hardness by forming Al-Fe intermetallics [5,7,9,13].…”

“…Diverse aluminized coatings have been obtained by hot-dipping carbon steels in Al [5,7,12,13] and Al-Si molten baths [5,9], 5Cr-0.5Mo steels in Al [14] and Al-Si molten baths [16], and 9Cr-1Mo steels in Al-Si [17] and Al-Si-Mg molten baths [15]. They significantly enhanced the high-temperature oxidation and corrosion resistance of the underlying steels through forming α-Al 2 O 3 [5,7,9,[12][13][14]17,18], α-Al 2 O 3 + FeAl [6,15], and FeAl [16] layers. However, microstructural changes during high-temperature oxidation and the oxidation resistance of 9Cr-1Mo steels that were hot-dipped in the Al molten bath have not been adequately investigated before.…”

Corrosion of Carbon Steel with and without Aluminized Coating in (O, S, H)-containing Gases at 500-800℃

“…5(a) shows ~ 200 µm-thick aluminized coating, which consisted of the Al-rich topcoat and Al-Fe alloy layer. The interface between the coating and the substrate was characterized by the uneven tongue-or finger-like morphology [9]. The formed scales were hardly recognizable, despite the corrosion in Ar/ 0.1%H 2 S gas and Ar/1%SO 2 gas (Figs.…”

“…The purity of Ar, SO 2 , and H 2 S gas was 99.9999, 99.95, and 99.95%, respectively. The Al coating was prepared by hot-dipping the carbon steel in molten Al bath at 800 o C for 10 min through the Al coating procedure described elsewhere [9]. The corroded samples were inspected by a scanning electron microscope (SEM) equipped with an energydispersive spectrometer (EDS), and an X-ray diffractometer (XRD).…”

Corrosion of Fe-9%Cr-1%Mo Steel at 600 and 700℃ in N2/(0.5, 2.5)%H2S-mixed Gas

“…The corrosion of T91 steel in H 2 /H 2 Smixed gas at 575-650 o C led to the formation of (FeS, FeCr 2 S 4 )-sulfide scales, which tended to crack and spall off during cooling [11]. Further study on the effect of H 2 S gas on corrosion is still needed, because the industrially important H 2 S gas is particularly destructive owing to the formation of the nonprotective metal sulfide scales and the hydrogen dissolution [12]. The purpose of this study is to investigate the hightemperature corrosion behavior of T91 steel in N 2 / H 2 S-mixed gas.…”