LANGMUIR FILMS OF CORROSION MODEL INHIBITORS IN PRESENCE OF OTHER PRODUCTION CHEMICALS IN OIL INDUSTRY

Interactions between monolayers of trilaurylamine (TLA) and various wa ter-soluble corrosion, hydrate and scale inhibitors, as well as acetic acid and FeCl2, have been studied by means of the Langmuir technique. The water-soluble compounds were present in the subphase before TLA w as spread. Their influence on the monolayer properties were measured b y means of surface pressure-area (pi-A) isotherms and constant surface pressure-area relaxation measurements. All the added water soluble sp ecies gave rise to monolayer expansion. The monolayer expansion observ ed for TLA at pH 1, increased when FeCl2 was added to the subphase at the same pH. Polyethyleneglycols with molecular weight higher than 200 destabilized totally the TLA-monolayer, probably due to bending and f olding into multilayers. Monolayer expansion and film instability incr eased with increased acetic acid concentrations. The destabilization m echanism in this case was most likely due to a combination of nucleati on and dissolution of film components into the subphase. The corrosion inhibitor Dyno KI 384 had a higher surface activity than TLA. Hence t he monolayer became unstable already at an addition of 0.7 ppm due to a high penetration into the film. Monolayer penetration of the scale i nhibitor by Dyno SI 427 seems to be concentration independent, but the monolayer rigidity increases upon penetration.