Method for delaying corrosion of fluorine ions to titanium material in ammonium sulfate wastewater evaporative crystallization process

The invention discloses a method for delaying corrosion of fluorine ions to a titanium material in an ammonium sulfate wastewater evaporative crystallization process, which comprises the following steps: respectively forming connecting holes in heat exchanger sides of a second-effect separator and a third-effect separator, connecting branch pipelines between the connecting holes and an ammonia water pipeline, and welding the branch pipelines at an inlet of a mother liquor tank to be connected with the ammonia water pipeline, ammonia water is continuously added into heat exchangers of a second-effect separator and a third-effect separator in a small flow manner, and ammonia water is added into a mother liquor tank; the pH values of the mother liquor tank, the second-effect condensate water and the third-effect condensate water are monitored, the pH value in the mother liquor tank is controlled to be 4 or above, the effluent pH values of the second-effect condensate water and the third-effect condensate water a