Abstract
The corrosion resistance of nickel-phosphorus (Ni-P) coatings and their mechanical properties in seawater have led inestigations into the development of new technologies and the replacement of some special alloys in equipment used in oil production, such as valves, tubing, sucker rod joints, pumps, riser, manifolds and subsea Christmas trees. These studies began with Brenner and Riddel who developed, in the 1940s, formulations for Ni-P deposition on carbon steel without using an electric current. Joint deposition of nickel and phosphorus on a metallic surface (carbon steel) without applying an external current is accomplished using cathodic reduction with hydrogen (H) from a reducing agent (sodium hypophosphite) and nickel salts. To assure good performance of a Ni-P coating, the deposit quality must be inspected and evaluated during the chemical deposition process or in the end product. The recommended test parameters are: thickness, layer uniformity, hardness, adhesion, porosity, corrosion resistance and chemical composition of the nickel-phosphorus coating. The purpose of this paper was to investigate the Ni-P coating process, to evaluate the b haviour of Ni-P in a saline environment using aqueous brine (3.5% - 30% sodium chloride by mass) and to present possible defects that could compromise the coating.
Highlights
One of the traditional techniques to maintain the mechanical characteristics of a material in the manufacturing of industrial equipment, primarily using carbon steel or low alloy steels, as well as to make surfaces more resistant to abrasion and corrosion, is without doubt, by applying a specific finish, such electroless nickel-phosphorus plating (Ni-P)
For a Ni-P coating applied on carbon steel come meet the adverse conditions of the production of petroleum products, it is essential to adopt a methodology critical inspection “in situ”, with due allowance for the manufacturing process of the equipment and the process of deposition based on ISO 4527 [20]
The corrosion resistance of Ni-P coating depends on the concentration of nickel and phosphorus present in the deposited layer and increasing the phosphorus content improves the anti-corrosion protection
Summary
One of the traditional techniques to maintain the mechanical characteristics of a material in the manufacturing of industrial equipment, primarily using carbon steel or low alloy steels, as well as to make surfaces more resistant to abrasion and corrosion, is without doubt, by applying a specific finish, such electroless nickel-phosphorus plating (Ni-P). The Ni-P coating is deposited on carbon steel without the application of an external electrical current This feature has led to, directly or indirectly, the development of special tools and new technologies in the area of oil production in a high salinity environment associated with corrosive gases such as CO2 and H2S. Studies by Duncan [4], Colaruotolo [5], Mainier et al [6], Tallinn [7], Weil et al [8], Mainier and Araújo [9], Delaunois et al [10], Liu et al [11] and Baudrand [12] have shown that the rate of growth and application of Ni-P coatings since the 1980s has increased in several industrial sectors The performance of this finish has led to its use in various industrial areas such as the production of pulp and paper, plastics, petrochemicals, textiles, automobiles, aeronautics, electronics and food. Carbide (SiC), Teflon, etc., which will provide new properties to Ni-P coatings and lead to new Industrial applications
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