Less severe chemical burns take around 3 to 4 weeks to heal while more severe chemical burns can take from 2 to 3 months to heal.
If the chemical burn hasn't healed up within a few months then you might want to speak with your doctor but as long as you've cleaned the chemical off properly that burned you and properly care for the chemical burn then it should be healed within 3 months minimum.
To help with the healing process of the chemical burn wrap the chemical burn area with some sterile dressing or gauze to protect it.