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Coupons for corrosion and scaling control
    The coupons are used as a main tool when corrosion control is carried out by the gravimetric method. As a rule, coupons are made of steel of the same grade as the pipeline steel where the corrosion control unit is installed or the same steel is used (usually steel 20) for all coupons. In our opinion, the second approach is more practical, because it allows to get comparable results on the corrosiveness of the media in relation to the same material. If different materials for the coupons are used, then there is the uncertainty regarding the factor which should be taken into account in a particular case, because carbon steels can differ in their corrosion resistance.
    There is another objection to using steel of the same grade as pipeline steel. According to the industrial tests which have been carried out by our experts on the pipelines of the oil-gathering system and the water supply lines (in the same media, at the same time) with various options “steel grade - pipe manufacturer”, corrosion rates of even the same steel grade of different factories can be quite deferent from each other, despite the fact that both steel are produced according to the same regulatory documents. Thus, not only the steel grade determines the resistance of the metal to corrosion. An indisputable factor is also the heat treatment, which may be different and accordingly the structure of steels will differ, which affects their corrosion resistance. Also there are other factors.
    In this regard, using the same material for coupons is more logical, and moreover, it should be purchased in quantity in order to minimize differences between supplied coupons. We adhere to this ideology, purchasing steel 20 in quantities sufficient to satisfy our own annual demand (about 6000 coupons per month) and third-party orders. At the same time, we can produce coupons from any steel grades which are available on the market, as well as coupons cut directly out the pipeline.
    The main dimensions of the manufactured coupons are as follows: cylindrical 14×11.1×9, 16×10×9, disk 28×11.1×3, flat 76.2×12.7×1.7, 80×20, 40×10×2 and others according to the customer’s requirements. There are also coupons for colonization by adherent bacteria, although any of them can be used for this (flat are more convenient). Flat coupons, which are made with holes of various diameters, are also used to control scaling. The intensity of salt deposition is determined depending on the size of areas that were covered with salt.