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Stepan Oilfield Solutions brings innovative, biodegradable corrosion inhibitor intermediates

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The corrosion of carbon steel tubing, pipelines and process equipment during oil and gas production can lead to substantial environmental and economic consequences. One of the proven and most widely used mitigation techniques is the addition of film-forming corrosion inhibitors into production streams. Those compounds have an affinity for metals and will form a film on the metal’s surface, creating an electric resistance between the metal and the corrosive species such as carbon dioxide or hydrogen sulfide.

Surfactants like alkyl dimethyl benzyl quat, imidazolines or phosphate esters have been widely used to tackle corrosion, but their ecotoxicity profile do not always meet the criteria determined by the OSPAR Convention.

This directive controls the release of chemicals in the North Sea and will attribute the best rating to the products achieving the following results:

  • Biodegradability above 60% after 28 days in marine water (OECD 306);
  • Toxicity: LC50 above 10 mg/l for the following marine species: algae (skeletonema costatum), crustacean (acartia tonsa), fish (scophtalmus maximus), sediment reworker (corophium volutator);
  • Bioaccumulation: Log Pow below 3. The molecular weight can also be important. For molecules above 700 g/mol, the potential to bioaccumulate is considered low because it is too large to cross cell membranes.

PETROSTEP® GCI Series, a new family of biodegradable diquat, has shown very good efficiency against corrosion in a sweet environment. The molecules have been specifically designed for this application:

  • Its core is made of a hydrophilic part that enhances the solubility of PETROSTEP GCI Series in water.
  • Its quaternary ammonium groups stick to the metal due to interaction with the anionic compounds present on the steel.
  • Its hydrocarbon chains also help repulse water and create a fatty film at the surface of the metal pipe.
  • The products in the PETROSTEP GCI Series can be adjusted to adapt to the various conditions in the field such as different salinity, pressure and temperature.
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The results from Bubble Test show that PETROSTEP GCI products at 6 ppm active reach up to 85% inhibition efficiency in standard brines such as NACE 3.5 and Forties at 80C.  When PETROSTEP GCI is formulated with 10% standard mercaptan synergist, the corrosion protection can be boosted up to 95%.

These molecules are also compatible with standard nonionic and cationic surfactants used in formulation to achieve even greater performance.

Thermogravimetric analysis on these compounds on their own shows no sign of weight loss until 135°C.

In addition, ecotoxicological testing on PETROSTEP GCI-1 found that it exhibits good biodegradability in marine water and its high molecular weight makes it a non-bioaccumulant.

PETROSTEP GCI Series of products is a superior, sustainable technology for mitigating your corrosion issues in North Sea operations and in the rest of the world.  

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