Corrosion Control In Oil And Gas Pipelines

The multielectrode array sensor (MAS) probe is ideally suited for monitoring corrosion rates in process streams. Multiple discrete elements or electrodes are used to replicate the material of interest. The MAS probe measures corrosion rates by assessing the current flow between coupled electrodes. The electrodes can be manufactured from a wide range of alloys and product forms. SwRI has used this method to monitor the corrosion of a variety of materials.

The wireless mobile sensor and the MAS probe sensor are just two examples of corrosion sensing and monitoring technologies. SwRI has developed a suite of corrosion sensing and monitoring devices. Significant inspection and repair costs can be avoided with the use of tools such as these.

Deposition Coatings
The deposition of material coatings can be effectively employed to protect surfaces of components from wear, erosion and corrosion. A variety of coatings have been studied including metals, ceramics and polymers. A number of deposition techniques have also been developed. One example is magnetron sputtering, where 20-30 µm thick Al-Ce-Co coatings are deposited on Al alloys and 1018 carbon steel, which is sufficient for most applications where corrosion and erosion are possible. A cross-section Al clad and Al-Ce-Co deposition coating is shown in Figure 7a and 7b, respectively. Microstructural analyses show that under certain deposition conditions, amorphous/nano-crystalline structures are obtained, which show superior corrosion resistance in electrochemical tests.

NOT FOUND: corr7.JPG
Figure 7. SEM cross-section of (a) Al clad and (b) amorphous AlCoCe coating

Diamond-like carbon (DLC) coatings can be produced using the plasma immersion ion deposition (PIID) process. The coatings are very hard and dense and can be applied to many components for increased wear and erosion resistance. In fact, SwRI recently developed a technique for applying DLC coatings to the inner surface of pipeline segments.

Ti-Si-C-N based nanocomposite coatings deposited using the Plasma Enhanced Magnetron Sputtering (PEMS) process have shown high-hardness (>40GPa) and superior erosion and wear resistance. PEMS was originally developed for use on gas turbine compressor blades and vanes and steam turbine blades against solid particle erosion and liquid droplet erosion, and won an R&D 100 award in 2009.

Laboratory tests have shown that the erosion resistance of these coatings can increase the lifetime by a few to more than 100 times as compared to uncoated substrates. The corrosion resistance for Ti-Si-C-N coated samples has been shown to be comparable to or better than the uncoated Ti-6Al-4V substrate, which already exhibits excellent corrosion resistance.

SwRI has developed a suite of deposition-coating solutions for addressing a range of erosion, corrosion and wear issues. As noted, large-scale production of corrosion-resistant coatings using vacuum deposition techniques is possible (e.g. Al-Co-Ce coatings and DLC coatings). For more severe environments, vacuum-deposited Ti-Si-C-N nanocomposite coatings have been successfully used to protect important components from erosion, abrasion and corrosion damage.