Abstract
The effects of micro-alloying of plain carbon steel with Cr and Mo on the corrosion behavior in CO2-saturated (sweet) brine (0.5 M NaCl, pH 6.6) environment, under hydrodynamic conditions, at 80°C were investigated. Crystalline siderite/chukanovite scales formed on all the alloys. Analysis of potentiostatic current transient data suggest that there exists a synergistic interaction between Cr and Mo, which induces more rapid crystallization of the scale compared to Mo-free steels. Increasing the Mo content also suppressed the transport-dependent dissolution current passing through the initially-present amorphous surface film. TEM images of the FIB-sectioned corrosion scales confirm that the corrosion scale formed on 1Cr0.7Mo is comparatively thinner and yet offers greater protectiveness when compared to the plain carbon steel.
Highlights
The development of high durability and low cost materials able to operate in a broad range of increasingly aggressive exposure conditions is critical for the oil and gas industries
By comparing the chronoamperometric behavior we hypothesize that the models for the plain carbon steel and the Cr/Mo micro-alloyed steels essentially follow the same pattern, with some modifications in their constituting components and that the variation depends on the type and level of micro-alloying
A possible mechanism is that of colloid-mediated crystal assembly or of organized attachment mediated by solution species, from an amorphous precursor or cluster.[35,36]
Summary
The development of high durability and low cost materials able to operate in a broad range of increasingly aggressive exposure conditions is critical for the oil and gas industries. The little information available in the literature under high flow conditions is often contradictory, mainly because of the different exposure conditions in terms of temperature and/or pH.[7,21,22,23,24,25,26,27] Our previous work[21] demonstrated that, at pH >6.5 and at 80◦C, anodic dissolution of plain carbon steel to form a colloidal product proceeded in parallel with an anodic electrocrystallization reaction that resulted in a crystalline scale.
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