in chemistry, any of several methods by which esters or salts of sulfuric acid (sulfates) are formed. The esters are commonly prepared by treating an alcohol with sulfuric acid, sulfur trioxide, chlorosulfuric acid, or sulfamic acid. The term sulfation often connotes a deleterious effect; an example is the accretion on statuary of unsightly films resulting from the action of airborne oxides or sulfur on calcium minerals in the stone. Another undesirable process called sulfation is the accumulation of a crystalline form of lead sulfate on the plates of lead–acid storage batteries.