The man was walking along Manston Road at 8.20pm and was attacked as he entered the St Laurence Graveyard, the churchyard of the St Laurence-In-Thanet Church in the village of St Lawrence.
He was rushed to hospital for treatment of burns to the back of his head. He remains there, but his injuries are not life-threatening.
The force is appealing for witnesses after an investigation was launched to establish the circumstances surrounding the incident.
No arrests have so far been made, as officers continue to hunt for the suspect.
More details about the “noxious substance” are yet to be disclosed.
District Commander for Thanet, Chief Inspector Ian Swallow, acknowledged the impact of such an incident on a community and confirmed there will be an increased police presence in the area while inquiries continue.
He said: “We would like to appeal to anyone who may have witnessed anything to get in touch.
“Anyone with dashcam or doorbell footage in the area from Margate Road, on to Newington Road and Manston Road, please could you check for anything that may help officers with the investigation.
“Incidents like these are rare, but we do not underestimate the impact it has on a community, and as a result, an increased police presence will be seen in the area as we continue to carry out enquiries.”
Anyone with information is asked to contact Kent Police on 01843 222289, quoting reference 46/23590/24.