A new and exciting technique for performing DLC deposition on the inside of cylindrical substrates, in particular pipes, will be described. Using the hollow cathode effect (HCE), a high density plasma can be generated within such cylindrical substrates by using Plasma Enhanced Chemical Vapor Deposition (PECVD). As the pipe itself is the vacuum chamber, such high density plasmas can be maintained by using asymmetric bipolar direct current (DC) pulsed power. Very high deposition rates can thus be achieved of the order of 1micron/min. A hydrocarbon precursor (C 2 H 2 ) is used to deposit thick DLC films which are inert and have a high corrosion resistance. Adhesion to the metallic substrate is improved by adding silicon to the DLC layer. These films also have excellent erosion and wear resistant properties and the process can be optimized depending on what film properties are most vital for whatever application the coating is required for. Corrosion and wear resistance are also improved by having a pure DLC layer on top of the deposited structure. The actual process and deposition system will be described in detail as well as how the technology works and how such high density plasmas can be maintained for various lengths and diameters of pipe. Testing of such novel DLC films was done by various techniques and results will be shown of hardness, adhesion, layer thickness, wear and corrosion resistance. A vast number of applications can greatly benefit from this novel process, on both a large and small scale. Examples of such applications would be industrial piping, offshore drilling, chemical delivery systems, gun barrels and medical devices.

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A novel technique for depositing thick DLC based films on the inside of cylindrical substrates, like pipes, tubes and valves, has been developed. A plasma enhanced chemical vapour deposition (PECVD) technique has been used to engineer and optimize the above mentioned films for maximum coating performance. Of particular importance is the corrosion and wear resistant qualities of these films. Changes in film chemistry, structure and thickness are attributed to the improved corrosion and wear resistance. Details will be given of the corrosion testing which has taken place, such as exposure to HCL (hot and ambient temperature), NaCl and H2S environments. One such test is a very aggressive sour autoclave test where the film is exposed to an aqueous, organic and gas phase over a 30 day period and no damage to the film was found. In depth details of this sour autoclave test will be shown including photographs of the film before and after testing. Wear testing has also been carried out in dry and wet sand slurry environments where very low coefficient of friction (COF) and wear rates were found. It is believed that this thick DLC based film can increase the component life in applications where internal surfaces are exposed to highly corrosive and abrasive media, in particular the oil and gas industry. Examples of such applications are mud pump sleeves, deep well components, directional drilling, abrasive flow spools, pump barrels and in sour fields (H2S).

Careful consideration of corrosion management during component manufacture is critical to protect assets over their useful field life. Recently, a new technology was introduced that can delay or mitigate the onset of corrosion on oil country tubular goods (OCTG) used in oil and gas production operations. The innovative method produces and applies a layered diamond- like-carbon (DLC) to the internal surface of OCTG tubulars by using a plasma enhanced chemical vapor deposition (PECVD) process. The technique makes use of the hollow cathode effect (HCE) to achieve a high deposition rate and a high ion bombardment rate. Initially developed for the coating of internal surfaces of piping with length:diameter aspect ratios less than 20, the process has recently been extended to high aspect ratio piping including OCTG. Its ion bombardment produces a dense barrier of a hard, wear and corrosion resistant DLC surface coating. The improvement in deposition rate and increase in thickness compared to earlier plasma coatings has enabled new applications such as corrosion and abrasion protection. Corrosion resistance is demonstrated based on exposure to HCl and NaCl environments. Mechanical properties include high hardness, high adhesion, and good wear resistance. The new technology enables a widespread use of DLC based coating and has significant potential to increase component life in applications where the internal surface of pipes are exposed to corrosive and abrasive environments especially in the oil and gas industry. The described surface treatment provides a new alternative to traditional polymer type coatings and/or increased alloy contents.