Production Engineering

Scaling on Critical Parts Phase 2: Experimental investigations of scale formation of deposits

During the extraction of natural gas or petroleum, the used structural components are exposed to many different strains and detrimental influences. One of these influencing variables is scaling with different organic or inorganic components of complex compositions, resulting in impairment of the functionalities of the structural components.
In a first step of this DGMK project, a literature research, based on the keyword 'lotus-effect', was performed to search suitable procedures for coating or modification of material surfaces of exceptionally critical processing parts for a better protection against scaling with organic or inorganic matter. In a second step, coaters were questioned about critical properties of different coatings concerning antiadhesive behaviour as well as different chemical and physical parameters and resistances. Two commonly used steel sheets (a Cr13 steel and slow-alloy steel comparable to API L80} and six different coatings (two DLCs, a dispersion coating of PTFE in nickel, an anti-graffiti coating and two different solid film lubricants) were selected due to their seemingly favourable properties. After coating of Cr13 steel sheets by the selected coaters, the coating systems were characterized by means of optical microscopy and SEM/EDX analyses on the surfaces as well as in cross sections. The formätion of inorganic scales on the surfaces of coated as well as on non-coäted surfaces using oversaturated solutions was experimentally determined and comparatively characterized for three chemical model systems (NaCI, KCI and BaSO₄). The results of these investigations show as a trend a relatively lower scale formation on DLC coatings pointing forward a possible coating for the purposes mentioned above. So, DLC coaters were questioned about the technical possibilities for a coating of a routinely used underground safety valve, showing that a given safety valve could be internally coated with a DLC only in segments.
A preselection of coatings for a possible reduction of scale formation seems possible. It must be noted that a critical examination of the coatings under the complex field conditions is necessary fora characterization of the suitability and resistivity.