A method of treating a crude oil containing no more than 5 wt. % water to inhibit inorganic fouling which comprises(a) introducing into the crude oil an effective amount of a water soluble antifoulant having the following formula: ##STR3## where R is selected from the group consisting of H and C;M is an alkaline earth metal;n is an integer ranging from 10 to 200; and(b) passing the crude oil conta