Erosion-corrosion is a dominant degradation in plant assets and influenced by various attributes of erodent such as velocity, corrosivity, shape, size, density, angle of attack and hardness, etc. Although Ni-P electroless coatings are famous for anti-corrosion and anti-wear properties; there is still room to improve these attributes that will pave its way towards various industrial applications. In this research work, various compositions of ternary Ni-P-graphene coatings were produced via the addition of different concentrations of graphene (30 mg/L, 60 mg/L, and 100 mg/L) into the electroless plating bath. Microstructural characterizations of coatings were conducted along with surface topography. Erosion-corrosion behaviors of the produced coatings were characterized using slurry pot erosion-corrosion testing employing AFS 50-70 Silica sand and 3.5 wt.% NaCl solution. The dominant wear mechanisms were identified using the SEM examination of surfaces after the erosion-corrosion test. High hardness, impermeability, and electrical properties of graphene concurrently improved the pure erosion, and erosion-corrosion attributes.
Erosion and erosion-corrosion are among the numerous degradations for piping and equipment in the hydrocarbon processing facilities.1-2 Erosion-corrosion is also known for versatility of failure modes (pitting, micro-cutting, under-deposit corrosion, gouging etc.).1,3 During erosion-corrosion, material loss rate is significantly higher than the sum of material loss rate due to pure erosion and pure corrosion acting separately. In certain instances, the shape and morphology of damaged surface and scale debris reveal tell-tale of damage mechanisms. 4 Some applications of carbon steel in the petroleum industry (e.g. alkaline sour water systems) require certain flow rate (10 fps – 20 fps) to manage cooling water corrosion as well as fouling deposits in case of heat exchangers. 1 Whereas higher velocities beyond 20 fps can jeopardize the integrity of carbon steel due to erosion and/ or erosion-corrosion damages.
Process equipment for oil sands processing (centrifuges, vessels etc.) and transportation (pumps, pipelines, valves etc.) are highly prone to erosion-corrosion and erosion damages. Erosion-corrosion and pure erosion are driven by number of factors that include (but not limited to) particle attributes (velocity, angle of attack, size, shape, weight/ density, hardness), material attributes (hardness, ductility, corrosion resistance, geometry) as well as service conditions (chemistry, corrosivity, temperature etc.). In the recent years, there have been considerable efforts to combat this degradation with detailed focus on each mitigation facet e.g., use of higher Mo containing alloys to resist organic acid corrosion or keeping higher corrosion allowances by allowing more wall thickness in design phase. Material up-gradations and surface modifications through re-designing are other possible solution to ensure the integrity of process equipment which in turn are accompanied by significantly higher capital costs. Coatings are among effective measures that can protect the material's surfaces by preventing the exposure to the environment and service conditions. Electroless Ni-P coatings are known for their better adhesion properties, and the absence of grain boundary (from amorphousness) is the reason for excellent corrosion resistance of Ni-P coatings. Moreover, the absence of solvents in electroless Ni-P coatings is another advantageous aspect that eliminates workmanship efforts in terms of drying and curing, etc. The downside of Ni-P coating is the potential wear under erosive environments which undoubtedly needs further attention of researchers.
