DLC coatings in high temperature hydrogen sulfide environment

Surface protection in high temperature hydrogen sulfide environment remains a significant challenge with limited number of materials providing adequate protection. Diamond-like carbon (DLC) thin films are recognized across different sectors as a promising way of controlling wear and the corrosion performance of components. The aim of this paper is to test the hypothesis that thin DLC coatings may act as an efficient corrosion barrier for steel components in high temperature hydrogen sulfide environment. The DLC coating was deposited in this work using Plasma-Enhanced Chemical Vapor Deposition (PECVD) process and the coating was characterized in terms of the structure morphology and mechanical properties. Coated test coupons were exposed to high pressure high temperature tests simulating sour production environments for the period of 28 days. The performance of DLC coating was compared with data obtained from a large tank lining joint industry project focusing on tank lining study previously completed by one of the authors

The effect of four commercially available steel decontamination processes on the performance of external coatings

External coatings used for corrosion protection often have to perform under severely corrosive environments. One major concern regarding coating performance is the negative effect of soluble salts on the steel substrate at the time of coating application, particularly for marine maintenance coating applications. These salts impact the ability of the applied coating systems to protect the steel in several ways including osmotic coating blistering, promotion of under-film metallic corrosion and coating disbondment. This paper focuses on removal of soluble salts contamination by commercially available decontamination processes in relation to external coating systems. We directly compare the effectiveness of four cleaning methods with the performance of ten coating systems. The methodology of surface contamination and preparation of test panels is discussed. After cleaning, sample evaluation for chloride ion contamination levels was carried out using Field method (commercial chloride ion test kit for surfaces) and Ion Chromatography method. Additionally, Scanning Electron Microscopy Energy Dispersive X-ray Spectroscopy (SEM/EDX) and elemental surface mapping analysis were carried out. Laboratory testing of coating systems included Adhesion, Porosity, Electrochemical Impedance Spectroscopy (EIS) analysis and cyclic UV/Salt Fog exposure. The performance of the ten coatings on all the substrates was good, but there were differences in gloss retention and on the degree of checking of the different coatings. The only significant difference in performance of the coatings compared to the method used for cleaning the substrate was higher undercreep observed for most of the coatings applied to the ultra-high pressure water jetted system. This shows the importance of substrate preparation due to the sensitivity of the coatings to even low levels of salt. Two coatings did not show increased undercreep and these may be more applicable for offshore maintenance applications where dry abrasive blasting is sometimes not used. The chemical treatment cleaning method used prior to coating application did not show any significant positive or negative effect on the performance of the applied coatings. The fact that the only differences in performance for the coatings applied to the differently prepared substrates was seen for undercreep suggests that the difference may be exacerbated for immersion situations. A follow up study to this one will examine the performance of internal coatings using immersion tests, and it will be interesting to see if these show increased effect on coating performance

DLC Coatings in Oil and Gas Production

Diamond-like carbon (DLC) coatings are recognized in many sectors as a promising way of controlling wear and the corrosion performance of components. DLC coatings are well established in the automotive industry where they are applied to the moving parts of direct injection fuel systems operating under frictional conditions at high pressures and in the aggressive environment of the combustion chamber. Over the last few years, there have also been an increasing number of reports of DLC coating applications in oil and gas production contexts, including in pipes, shut-off gates and various types of valves. This paper reviews current efforts to use DLC coatings in the oil and gas sectors and analyses typical coating degradation mechanisms including wear and wear-accelerated corrosion regimes. DLC coating deposition techniques including Physical (PVD) and Chemical Vapor Deposition (CVD) techniques are elaborated and the unique coating properties obtained from those two methods are assessed. Surface functionalization is discussed including dopants (W and Si) and gradient interlayers. Finally, the outlook for future use of DLC coatings in oil and gas production is discussed

OpenSense: An open-source toolbox for inertial-measurement-unit-based measurement of lower extremity kinematics over long durations

Background: The ability to measure joint kinematics in natural environments over long durations using inertial measurement units (IMUs) could enable at-home monitoring and personalized treatment of neurological and musculoskeletal disorders. However, drift, or the accumulation of error over time, inhibits the accurate measurement of movement over long durations. We sought to develop an open-source workflow to estimate lower extremity joint kinematics from IMU data that was accurate and capable of assessing and mitigating drift. Methods: We computed IMU-based estimates of kinematics using sensor fusion and an inverse kinematics approach with a constrained biomechanical model. We measured kinematics for 11 subjects as they performed two 10-min trials: walking and a repeated sequence of varied lower-extremity movements. To validate the approach, we compared the joint angles computed with IMU orientations to the joint angles computed from optical motion capture using root mean square (RMS) difference and Pearson correlations, and estimated drift using a linear regression on each subject’s RMS differences over time. Results: IMU-based kinematic estimates agreed with optical motion capture; median RMS differences over all subjects and all minutes were between 3 and 6 degrees for all joint angles except hip rotation and correlation coefficients were moderate to strong (r = 0.60–0.87). We observed minimal drift in the RMS differences over 10 min; the average slopes of the linear fits to these data were near zero (− 0.14–0.17 deg/min). Conclusions: Our workflow produced joint kinematics consistent with those estimated by optical motion capture, and could mitigate kinematic drift even in the trials of continuous walking without rest, which may obviate the need for explicit sensor recalibration (e.g. sitting or standing still for a few seconds or zero-velocity updates) used in current drift-mitigation approaches when studying similar activities. This could enable long-duration measurements, bringing the field one step closer to estimating kinematics in natural environments.Biomechatronics & Human-Machine Contro