Preparation of Ni-P electroless and its corrosion resistance against sea water

Electroless coating is much appropriate process at engineering surface. Since the discovery of electroless nickel-phosphorus coating in 3996, due to technical and economic advantages as well as desirable characteristics such as resistance to corrosion, abrasion and a high hardness has found wide application at engineering industries. Properties of electroless nickel-phosphorus coating depend on the characteristics of the used bath and heat treatment. In this study, optimal conditions and concentration of sodium citrate, sodium acetate and lactic acid in the bath of electroless nickel-phosphorus coating to the steel ck67 surface was determined. Structure, chemical composition and phases occurring in the coating were investigated using Scanning Electron Microscope (SEM) and X-ray diffraction analysis (XRD). The corrosion behavior of coatings in solution 3.5٪ NaCl was studied using electrochemical. The results showed that corrosion resistance of the coating with composition sodium citrate, sodium acetate and lactic acid decreased respectively.

Corrosion of stainless steel components in seawater reverse osmosis desalination plants-investigations on adapted internal cathodic protection

Stainless steel is widely used in seawater reverse osmosis units (SWRO) for both good mechanical and corrosion resistance properties. However, many corrosion failures of stainless steel in SWRO desalination units have been reported. These failures may often be attributed to un-adapted stainless steel grade selection and/or to the particular aggressive seawater conditions in "warm" regions (high ambient temperature, severe biofouling, etc.). Cathodic protection (CP) is a well-known efficient system to prevent corrosion of metallic materials in seawater. It is successfully used in the oil and gas industry to protect carbon steel structures exposed in open-sea. However, the specific service conditions of SWRO units may seriously affect the efficiency of such anti-corrosion system (high flow rates, large stainless steel surfaces affected by biofouling, confinement limiting protective cathodic current flow, etc.). Hence, CP in SWRO units should be considered with special care and modeling appears as useful tool to assess an appropriate CP design. However, there is a clear lack of CP data that could be transposed to SWRO service conditions (i.e. stainless steel, effect of biofouling, high flow rate, etc.). From this background a Join Industry Program was initiated including laboratory exposures, field measurements in a full scale SWRO desalination plant, and modeling work using PROCOR software. The present paper reviews the main parameters affecting corrosion of stainless steel alloys in seawater reverse osmosis units. CP on specific stainless steel devices was investigated in order to assess its actual efficiency for SWRO units. Severe environmental conditions were intentionally used to promote corrosion on the tested stainless steel products in order to evaluate the efficiency of CP. The study includes a modeling work aiming at predicting and designing adapted CP protection to modeled stainless steel units. An excellent correlation between modeling work and field measurements was found.

Galvanic corrosion of two non noble dental alloys

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Effects of Nd on the microstructures, mechanical properties and in vitro corrosion behavior of cast Mg-1Mn-2Zn-xNd alloys

Effects of neodymium (Nd) on the microstructures, mechanical properties, in vitro corrosion behavior, and cytotoxicity of as-cast Mg- 1Mn-2Zn-xNd alloys (x = 0.5, 1.0, 1.5, mass%) have been investigated to assess whether Nd is an effective element to increase the strength and corrosion resistance of Mg alloys, and to evaluate whether those alloys are suitable for biomedical applications. The microstructures were examined by X-ray diffraction analysis and optical microscopy. The mechanical properties were determined from uniaxial tensile and compressive tests. The corrosion behavior was studied using electrochemical measurement and cytotoxicity was evaluated using osteoblast-like SaOS2 cell. The results indicate that all the cast Mg-1Mn-2Zn-xNd alloys are composed of both alpha phase of magnesium (Mg) and a compound of Mg7Zn3, and their grain sizes decrease with Nd content. Nd is not an effective element to improve the strength and corrosion resistance of cast Mg-Mn-Zn alloys. Increase of Nd content from 0.5 to 1.5 does not significantly change biocompatibility of alloys. The cast alloys exhibit much better corrosion resistance than pure Mg and good biocompatibility.

Synergistic corrosion inhibition of mild steel in aqueous chloride solutions by an imidazolinium carboxylate salt

Mild steel infrastructure is constantly under corrosive attack in most environmental and industrial conditions. There is an ongoing search for environmentally friendly, highly effective inhibitor compounds that can provide a protective action in situations ranging from the marine environment to oil and gas pipelines. In this work an organic salt comprising a protic imidazolinium cation and a 4-hydroxycinnamate anion has been shown to produce a synergistic corrosion inhibition effect for mild steel in 0.01 M NaCl aqueous solutions under acidic, neutral, and basic conditions; an important and unusual phenomenon for one compound to support inhibition across a range of pH conditions. Significantly, the individual components of this compound do not inhibit as effectively at equivalent concentrations, particularly at pH 2. Immersion studies show the efficacy of these inhibitors in stifling corrosion as observed from optical, SEM, and profilometry experiments. The mechanism of inhibition appears to be dominated by anodic behavior where dissolution of the steel, and in particular the pitting process, is stifled. FTIR spectroscopy provides confirmation of a protective interfacial layer, with the observation of interactions between the steel surface and 4-hydroxycinnamate.