Method for reducing or preventing corrosion or fouling caused by acidic compounds

A method for reducing or preventing corrosion or fouling in an apparatus for carrying out a chemical process, where the corrosion or fouling is caused by acidic compounds present in the chemical process, which chemical process is a crude oil refinery process, a petrochemical process or a steam generating process, which method comprises the addition of at least one quaternary ammonium hydroxide of the formula (I) to the apparatus, wherein the chemical process is carried out:

• where
• R1, R2, R3 are each independently C1-C6 alkyl;
• R4 is C2-C18 alkyl;
• R3 and R4 together with the nitrogen atom may also form a 5 or 6-membered, saturated nitrogen heterocycle, which is unsubstituted or carries 1 or 2 methyl groups
• where the chemical process is a crude oil refinery process or a petrochemical process and comprises the addition of the compound of the formula (I) into at least one unit selected from the crude oil atmospheric distillation unit, the crude oil vacuum distillation unit, the visbreaker unit, the delayed coker unit, the fluidized catalytic cracking unit, the reformer unit, the hydrocracker unit, the alkanolamine unit, the sulfinol unit and the hydrodesulfurization unit, or where the chemical process is a steam generating process and comprises the addition of the compound of the formula (I) into the aqueous system of the boiler or steam generator;
• and where the acidic compounds causing corrosion or fouling in the chemical process are selected from the group consisting of hydrogen halides, hydrogen sulfide, hydrogen cyanide, thiocyanic acid, sulfuric acid, SO2, SO3, acidic ammonium salts and mixtures thereof.