I appreciate if somebody recommends a concrete sealant product that can be applied to cured concrete.
The sealant has to provide protection against chloride ingress and acceptable for contact with petroleum products (i.e. oil and gasoline).
That would depend on where he is in the world. When I google "Master Buider's Association", all references are to the Australian organisation of that name. The same will be true of coatings suppliers. In the US, probably Porter, Carboline, BASF, Sika would be appropriate.