Effect of sol-gel ZrO2 films on corrosion behavior of the 304 stainless steel in coal-gases environment at high temperature

In this work, ZrO2 films were prepared on 304 stainless steel surface through the sol gel method by sintering at 600 degrees C. The crystal structure and the surface morphology of films were characterized by X-ray diffraction and X-ray photoelectron spectroscopy. The corrosion resistances of uncoated and coated specimens were studied by high-temperature corrosion tests. During the test, samples were 'exposure to CO2-CO-CH4-H-2-H2S gases of coal during gasification at 600 degrees C, 700 degrees C and 800 degrees C. The results showed that corrosion pits and cracks in the stainless steel surface were caused by intergranular corrosion and thermal cracking. Furthermore, carbides and sulfides accelerated the intergranular corrosion of the samples, shortening the service life of the samples. No significant damage was observed on sample surfaces coated with ZrO2 films at test temperatures of 600 degrees C and 700 degrees C. When this temperature was raised to 800 degrees C, the slight intergranular corrosion was observed on the sample surface. At 700 degrees C, carbides and sulfides did not react with zirconia under the normal oxygen partial pressure, protecting the stainless steel matrix and enhancing the corrosion resistance of the matrix.