Why is my Pickled Corn not sour?

I made pickled corn the old-fashioned way by putting the corn in a salt brine in a crock jar. I used the ratio of 1 cup of salt to a gallon of water for the brine. I waited for 6 wks. before I tried to eat any of it. Now, it is very salty, but not sour like it is suppose to be. Does anyone know why this happened?