In order to cure efflorescence you have to stop either of the three things that it needs to manifest itself:
Water
Source of the salts
The route.
Cut any one of the 3 off and the efflorescence is sorted. If you wet it the problem will exacerbate. If you clean and efflorescence appears simply brush it with a dry brush. Wet it with anything and you feed it! Efflorescence prevention is better than cure.
Kevin