Biocide-mediated corrosion of coiled tubing.

Coiled tubing corrosion was investigated for 16 field water samples (S5 to S20) from a Canadian shale gas field. Weight loss corrosion rates of carbon steel beads incubated with these field water samples averaged 0.2 mm/yr, but injection water sample S19 had 1.25±0.07 mm/yr. S19 had a most probable number of zero acid-producing bacteria and incubation of S19 with carbon steel beads or coupons did not lead to big changes in microbial community composition. In contrast other field water samples had most probable numbers of APB of 102/mL to 107/mL and incubation of these field water samples with carbon steel beads or coupons often gave large changes in microbial community composition. HPLC analysis indicated that all field water samples had elevated concentrations of bromide (average 1.6 mM), which may be derived from bronopol, which was used as a biocide. S19 had the highest bromide concentration (4.2 mM) and was the only water sample with a high concentration of active bronopol (13.8 mM, 2760 ppm). Corrosion rates increased linearly with bronopol concentration, as determined by weight loss of carbon steel beads, for experiments with S19, with filtered S19 and with bronopol dissolved in defined medium. This indicated that the high corrosion rate found for S19 was due to its high bronopol concentration. The corrosion rate of coiled tubing coupons also increased linearly with bronopol concentration as determined by electrochemical methods. Profilometry measurements also showed formation of multiple pits on the surface of coiled tubing coupon with an average pit depth of 60 μm after 1 week of incubation with 1 mM bronopol. At the recommended dosage of 100 ppm the corrosiveness of bronopol towards carbon steel beads was modest (0.011 mm/yr). Higher concentrations, resulting if biocide is added repeatedly as commonly done in shale gas operations, are more corrosive and should be avoided. Overdosing may be avoided by assaying the presence of residual biocide by HPLC, rather than by assaying the presence of residual surviving bacteria

Comparison of the scuffing behaviour and wear resistance of candidate engineered coatings for automotive piston rings

Continuous optimization of advanced coatings is required to achieve technology advances and strict emission standards in automotive systems. Integration of conventional ceramic coatings and hard amorphous graphite-like carbon (GLC) with low friction is an economically feasible way of achieving superior efficiency of oil and durability as well as scuffing resistance. This work evaluates the scuffing resistant capacity and durability of engineered coating materials. The presence of GLC not only combats the scuffing damage and running instability effectively for conventional chromium-based coatings, and also improves the reliability and robustness of the piston rings. The scuffing mechanism of the engineered rings with and without GLC surface will be discussed by the observation of the damaged characteristics and the chemistry of the rubbing parts. This will potentially benefit to optimize the coating material in the piston assembly of engine

Tribological performance of CrN and CrN/GLC coated components for automotive engine applications

Modern automotive systems strictly demands increased mechanical and thermal loads, a longer service life and the weight reduction. Low friction hard coatings are extensively used in power train and engine applications by wear inhibition and friction reduction. The present study evaluates friction and wear responses of CrN and CrN/GLC coatings in different lubricated conditions. Results showed that, the presence of GLC surface not only lowered friction significantly by 67% under oil-starved or even dry conditions, but also obtained a pronounced decrease in wear by 70% for the opposite surface in the oillubricated environment, as compared to CrN coating. GLC application thus allowed the engine components to operate more reliably and durably when improper conditions happened. A tribochemical layer with the responsive character accounted for superior performance of GLC/CrN coating, which derived from the interactions of the additive in oil with the rubbing surfaces. The information on the correlation of performance with physics and chemistry of the rubbing interface was provided

Biocide-mediated corrosion of coiled tubing - Fig 5

<p>(a) Equivalent circuit used for simulating experimental impedance results (b) Nyquist and (c) Bode plots for EIS analysis of coiled tubing coupon WEs, incubated with 0 to 2.5 mM of bronopol in CSBK medium for 24 h. The reference electrode used was Ag/AgCl/3.5 M KCl.</p

Optical profilometer image and pit depth profile for CT coupon in the (a) absence and (b) presence of bronopol (1 mM) after one week of incubation with N₂-CO₂ headspace.

<p>Optical profilometer image and pit depth profile for CT coupon in the (a) absence and (b) presence of bronopol (1 mM) after one week of incubation with N₂-CO₂ headspace.</p

Microbial community compositions derived from Illumina-sequenced amplicons obtained from incubations of field water samples S5 to S19 with carbon steel beads or coiled tubing coupons (entries #9, 14, 16–20 and 22–37) or from incubations with sample S19 (entries #1–8, 10–13, 15, 21).

<p>The latter incubations were mostly as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181934#pone.0181934.t002" target="_blank">Table 2</a>. The estimated concentrations of bronopol in these incubations are given. Fractions of predominant taxa (% of total sequence reads) are shown. Fractions in excess of 1% are shaded. A rank identifier (#) and sequence ID are also given. The similarity of community compositions is indicated in a Bray-Curtis dendrogram with the vertical line drawn at 18% sequence divergence (bar is 10% sequence divergence).</p

Fitted EIS electrochemical parameters for CT coupon WEs incubated at different bronopol concentrations for 24 h.

<p>The tabulated data were derived from single incubations.</p

Schematic of field water sample types obtained from a CT operation.

<p>SP1, source water; SP2, injection water; SP3, produced water prior to passing through test separators; SP4, produced water after passing through test separators. The dotted line represents the surface. Injection water (rightward pointing arrows) in the CT will pick up NaCl and ammonium when water flows past the milling bit and returns to surface as produced water (leftward pointing arrows) in the CT annulus (the space between the production tubing and the CT).</p

Corrosion rates of carbon steel beads as a function of active bronopol concentration.

<p>Beads (five per incubation) were incubated for 30 days with field injection water sample S19 (↑), with S19 with additional bronopol or with dilutions of S19 with CSBK (black symbols), with S19_F an 0.2 μm filtrate of S19 (↓) or with dilutions of S19_F with CSBK (green symbols), or with CSBK medium with 0 to 10 mM (0 to 2000 ppm) of bronopol added (pink symbols). Detailed conditions for all 19 incubations are given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181934#pone.0181934.t002" target="_blank">Table 2</a>. Data are averages for two incubations with 5 beads each; SD is shown when this exceeded the size of the symbols.</p

Summary of results of potentiodynamic polarization scanning for CT coupon WEs incubated at different bronopol concentrations for 24 h.

<p>The tabulated data were derived from single incubations.</p