Abstract: During the production and operation, the discharge pipe was blocked by the collapsed refractory from the top of preheater C5 cyclone. On-site observation revealed that there was serious anchor corrosion in the integrated area with refractory materials. Research analysis was conducted on anchor corrosion, quality control during refractory material construction, process design and production operation, and it turned out that serious high temperature corrosion on anchor was caused by high chlorine in its environment and high construction quality would help isolate chlorine from the anchors as well.