The effects of Na, K, and Fe with porous cordierite were investigated at elevated temperatures. Samples of unused diesel particulate filter cordierite substrates were doped with sodium, potassium, and iron. The doped samples were heated in a thermal gravimetric analyzer to 300, 500, 900, and 1100 A degrees C. The resulting interactions were analyzed with scanning electron microscopy, wavelength-dispersive X-ray spectroscopy (WDS), and X-ray diffraction. The alkalis and iron induced corrosion and degradation to the cordierite substrate at temperatures lower than pristine cordierite substrate samples. The corrosion and degradation pathway followed the porous structure as observed with WDS.