Corrosion behaviors of AISI 1025 steels with electroless nickel/aluminized coatings in NaCl-induced hot corrosion

Three types of coatings, electroless nickel coating (EN), hot-dip aluminum with added silicon coating (HD) and pack aluminide coatings (PC), on low carbon steel were deposited with 2 mg cm(-2) NaCl and oxidized at 850 degreesC for 1-169 h isothermally. The results showed that-all types of coatings could improve high-temperature, corrosion resistance. The aluminized coatings (HD and PC) had rather lower corrosion rates than that of EN coating; moreover, the HD exhibited the best corrosion resistance. The preoxidation treatment of PC apparently improved the corrosion. resistance, while that of HD had an adverse effect due to the formation of cracks,in the brittle Fe2Al5 layer during heating and cooling. The HID is applicable to long-term exposure owing to its abundant aluminum providing for the formation of protective alumina, while the PC is not suitable. The PC, however, is applicable to cyclic short-term corrosion in NaCl-containing environments at high-temperatures. (C) 2003 Elsevier B.V. All rights reserved.