EFFECT OF IRON SULFIDE ON CO2H2S CORROSION AND

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EFFECT OF IRON SULFIDE ON CO2H2S CORROSION AND Powered By Docstoc
					     EXPERIMENTAL EVALUATION OF CORROSION INHIBITOR PERFORMANCE IN
            PRESENCE OF IRON SULFIDE IN CO2/H2S ENVIRONMENT


        Mohsen H. Achour, Juri Kolts, Phillip Humble, Roger Hudgins,
                              ConocoPhillips
                         Mohsen.h.achour@conocophillips.com



Abstract


When iron sulfide (FeS) film coats a carbon steel surface, it can affect the extent of
corrosion and corrosion inhibition in several ways. A laboratory experimental set up has
been designed and used to study such effects. The apparatus provides various
techniques of measuring the corrosion rate of FeS coated and uncoated steel surfaces in
presence of an oil/brine solution containing CO2 and H2S. The film is build in-situ by two
distinct methods, either through reacting the H2S present in the system with an iron
chloride (FeCl2) aqueous solution injected into the corrosion cell, or by pre-corroding the
steel surface with a CO2/H2S saturated uninhibited brine.


The newly designed set up was validated in terms of the system dynamics, the FeS
formation and deposition, the H2S safety controls/monitoring and the corrosion measuring
techniques installed in the system. Results show that the film formed in situ is 100% iron
sulfide of Mackinawite type according to the SEM and XRD analyses performed after the
test. In uninhibited systems, the iron sulfide film provides a certain protection against
general corrosion but can be the basis for pitting occurrences. In inhibited systems, the
protection is ensured through absorption of the inhibitor into the FeS film and reaching the
steel surface. The particle size distribution of the film has been measured and confirms
the importance of the large surface area provided by the film. Such test has been proven
to assess the performance of corrosion inhibitors in presence of iron sulfide in the system.




NACE 2008