A conversion coating on carbon steel with good anti-wax performance in crude oil

Wax deposition on pipeline from crude oil is a prevalent problem that petroleum industry has always been suffered. In this paper, a conversion coating on carbon steel with good anti-wax performance was constructed to solve this problem through a simple coating and heat treatment process. The conversion coating is composed of pyrophosphate with a flower-like microstructure. After wax deposition test, the conversion coating has low wax deposition weight which is 2.9 mg/cm2 and high wax deposition reduction rate (80% in average). The conversion coating has a special wettability which is superoleophobic with low oil-adhesion in water (oil contact angle is 162° and rolling angle is 7°) and hydrophilic in oil. The anti-wax mechanism is discussed and it may be attributed to the polar hydrophilic component and micro-structure of the conversion coating.