Corrosion Resistance Of Stainless Steels Exposed To Aggressive Environments With Particles And Water

The present work describes the corrosion studies (using electrochemical techniques) of coated and uncoated steels exposed to corrosive mixtures (including 6% ferric Chloride, alcohols, particles and water). Open Circuit Potential (OCP), Cyclic Potentiodynamic Polarization (CPP) and a modified version of the Zero Resistance Amperometry (ZRA) testing methodology were proposed to compare the corrosion resistance of several steel exposed to these environments. The modified version of the ZRA is not only measured accurately (within 1^{oThe CPP tests in 316 SS showed that the addition of the sand decreased the Pitting Potential in 316 Stainless Steels by about 130 mV_{SCEINTRODUCTION: Recently, due to the increasingly high demand for oil, drilling in deeper and harsher environments had opened a window of opportunities to existing engineering materials exposed to more aggressive environments. New methodologies are being developed to assess the risk for failure of coated carbon steels, coated and uncoated arsenic stainless steels (SS) and uncoated highly alloyed steels. The main objective is to predict the performance of these materials in very harsh applications. A thorough understanding of the corrosion properties of these materials exposed to these complex fluids (mixtures of fluids that include corrosive agents and particulates) is desirable to facilitate safety. Inexpensive carbon steels and austenitic stainless steels (type 304 and 316) are the typical choice for most industries to produce components for downhole applications. However, in harsher conditions, Duplex Stainless Steels (DSS) as well as highly alloyed steels (including Ni alloys) are typically used to guarantee longer service life. However, any materials containing Ni is currently in high demand and therefore every attempt is made to limit the amount of Ni in any material that needs it for harsh environment.}. However, in the 25-Cr DSS the only effect observed was an increase in the passive current (no pitting was observed at this temperature). The abrasion testing of different coated steels in 3.5% NaCl with and without additions of sand particles at very high speed (rotation experiment) was used to characterize the coating performance in these environments. As expected, the carbon steels presented very high currents (thousands of microAmps) once the coating was compromised (after the rotation started). Similarly, the Stainless Steels (SS) type 303 and 316 showed high currents (hundreds of microAmps) once the coating was compromised (after the rotation started). When the same coating (Epoxy A) is applied to 304 SS sample, exposed to a mixture of 90% Mono-Ethylene Glycol and 10% deionized water (DI H₂O) (without rotation) and increased the temperature, the coating breaks down at higher temperatures (increase in the current and drop in the potential measured). Ongoing work is aiming at understanding what is the critical temperature and rotational speed for these types of coatings.} C) the Critical Pitting Temperature (CPT) on the different alloys studied (metallic bars exposed to 6% Ferric Chloride), but also allowed to perform the testing in a very short time. This technique is a promising way to characterize and rank different materials subjected to the same environmental conditions.