Characterization of phosphate conversion layers by combined Auger electron spectroscopy and X-ray microanalysis

Combined high-resolution AES and EDX studies have been performed of a number of industrial phosphate conversion layers on steel in order to determine the importance of the surface composition for the corrosion protection of the phosphated steel.

The well-known Cr(III) rinse of zinc-iron phosphate which improves its long-term paint adhesion performance was found to result in an exchange of Zn²⁺ with Cr³⁺ ions in the surface layers of the crystals. Corrosion improvement is caused by a slower rate of attack of the Cr-containing crystals due to the low solubility of CrP0₄ in aqueous media.

A commercial calcium-zinc-iron phosphate system was studied for corrosion resistance in relation to its conditions of formation. Phosphate layers with optimum corrosion resistance were found to have a strongly enriched iron content in the surface layers.     

Effects of the supporting electrolyte on the kinetics of the removal of proteins adsorbed on a stainless steel surface by H2O2-electrolysis

The effects of different types of supporting electrolytes on the removal of beta-lactoglobulin (beta-Lg) after being adsorbed to a stainless steel surface by a H2O2-electrolysis treatment was investigated. In this process, hydroxyl radicals (*OH), generated by the electrolysis of hydrogen peroxide, decompose the substances adhering to the surface. The removal of the adsorbed protein from the stainless steel surface during the treatment was monitored in situ by ellipsometry. The apparent first-order removal rate constants, k(cl), for 17 types of supporting electrolytes were determined, as well as the current corresponding to the rate of generation of *OH. The k(cl) and generated current values for LiCl, NaCl, KCl, KNO(3), K(2)SO(4), CH(3)COOK, and K(2)CO(3) were all similar. Ca(2+) and Mg(2+) strongly suppressed the removal of the adsorbed protein. The presence of ammonium compounds led to an increase in k(cl) and current values. In H2O2-electrolysis in the presence of potassium phosphate, the removal was extremely rapid, and an apparent increase in the thickness of the adsorbed layer was observed. The mechanisms responsible for the peculiar effects of calcium, magnesium, phosphate, and ammonium compounds were investigated by means of a Fourier transform infrared (FTIR) spectroscopic analysis, as well as by the characteristics of the removal under different treatment conditions.     

Conducting polyaniline/nano-zinc phosphate composite as a pigment for corrosion protection of low-carbon steel

Zinc phosphate (Zn₃(PO₄)₂) nanocrystals were synthesized and used for making conducting polyaniline/nano-zinc phosphate composite by chemical oxidative method. The product was characterized by UV–visible absorption spectroscopy. The crystal structure, morphology and thermal stability of the product were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and thermo gravimetric analysis, respectively. The epoxy-based paint containing conducting polyaniline/nano-zinc phosphate composite pigment was applied on low-carbon steel samples. Corrosion protection performance of the painted low-carbon steel samples in 3.5 mass % sodium chloride solution was evaluated using electrochemical technique. Transmission electron microscopic image revealed the formation of core shell structure of the composite. Composite was found to be more thermally stable than the conducting polyaniline. The corrosion rate of conducting polyaniline/nano-zinc phosphate-painted low-carbon steel was found to be 5.1 × 10^?4 mm per year, about 34 times lower than that of unpainted low-carbon steel and 10 times lower than that of epoxy nano-zinc phosphate paint-coated steel. The study reveals the possibility of using conducting polyaniline/nano-zinc phosphate as a pigment for corrosion protection.     

Aggregation Properties of Sodium Hyaluronate with Alkanediyl-alpha,omega-bis(dimethylalkylammonium Bromide) Surfactants in Aqueous Sodium Chloride Solution

Lysine, which is an amino acid with a basic side group, is present in biological fluids and its role in the biological calcification process was investigated. It was found to inhibit the crystal growth rate of hydroxyapatite (HAP), in solutions supersaturated only with respect to this calcium phosphate salt and this rate reduction was attributed to adsorption and further blocking of the active growth sites on the crystal surface. The crystallization kinetics were interpreted in terms of the Langmuir adsorption model. The apparent order of the crystallization reaction was found to be n=2, suggesting a surface diffusion controlled spiral growth mechanism. Kinetic results of HAP crystallization were obtained using the constant composition method where the concentration of the reactants is kept constant during the course of the crystal growth experiment. Copyright 2000 Academic Press.     

A3钢在缓蚀颜料提取液中的EIS研究

应用EIS研究了A3钢在不同 pH值的磷酸锌或三聚磷酸铝 3.5 %NaCl提取液中的腐蚀行为 .结果显示 ,相同条件下 ,A3钢的电阻值随溶液 pH值增加而增加 ,电容值则相反 .在磷酸锌3.5 %NaCl提取液中 ,因磷酸锌的溶解度太小 ,没有足够的量对金属基底A3钢进行有效的保护 .在 pH值为 6的三聚磷酸铝 3.5 %NaCl提取液中 ,A3钢表现出较明显的缓蚀现象 ,可能是因为三聚磷酸根离子与腐蚀产物Fe2 + 、Fe3+ 络合并在钢表面形成了一层致密的保护膜 ,从而有效地阻止了腐蚀介质的进一步入侵 .防蚀颜料的溶解度大小是决定它的缓蚀性能优劣的重要因素之一     

Corrosion resistance of amorphous AlPO4 coating in salty atmospheres

The objective of the present study was to introduce a cost-effective and environmentally friendly coating to improve the corrosion resistance of the structures located in salt water. The coating solution, based on amorphous aluminum phosphate composition, was synthesized by sol–gel process and applied to AISI 304 stainless steel by dip coating technique. X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy analyses were employed to investigate the phase composition and morphology of the coating. Corrosion behavior of the uncoated and coated samples was investigated using standard salt spray test, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. Salt spray test results for the bare substrate revealed a corrosion rate of six-time greater than that of the coated surface after 168 hr exposure time. Electrochemical test results declared that the amorphous AlPO₄ coating decreased the corrosion current density of the AISI 304 stainless steel by 10 orders of magnitude. Furthermore, according to the corresponding EIS measurements, the coated surface exhibited a superior anti-corrosion performance than uncoated sample. Overall, the results declared that the amorphous AlPO₄ coating could be a good choice for surface protection of stainless steel against electrochemical corrosion in salty environments.     

Effect of phosphate ion on filtration characteristics of solids generated in simulated high level liquid waste

The effect of phosphate ion on the filtration characteristics of solids generated in a high level liquid waste was experimentally examined. Addition of phosphate ion into the simulated HLLW induced the formation of phosphate such as zirconium phosphate and phosphomolybdic acid. The filtration rate of zirconium phosphate abruptly dropped in the midst of filtration because of a gel-cake formation on the filter surface. The denitration of the simulated HLLW contained zirconium phosphate improved the filterability of this gelatinous solid. The filtration rates of denitrated HLLW decreased with increase of the phosphate ion concentration, since the solids formed by denitration had irregular particle size and configuration in the simulated HLLW with phosphate ion. To increase the filtration rate of denitrated HLLW, a solid suspension filtration tester was designed. The solid-suspension accelerated the filtration rate only in the simulated HLLW with more than 1500 ppm phosphate ion concentration. Under this condition, the simple agitation can easily suspend the constituent solids of filter cake in the solution and a much higher filtration rate can be obtained because the filter cake is continuously swept from the filter surface by rotation of propellers.     

Effect of phosvitin on the nucleation and growth of calcium phosphates in physiological solutions

The promoting effect of phosvitin on the nucleation of hydroxyapatite (HAP) and the inhibitory effect of phosvitin on the transformation from amorphous calcium phosphate (ACP) to HAP were investigated. Atomic force microscopy observations showed that the nucleation of HAP on collagen substrate was greatly enhanced when the phosvitin was bound on the collagen surface. Nucleated crystals were uniformly distributed with a high nucleation rate on the collagen surface in the presence of phosvitin, while, in the absence of phosvitin, crystals nucleated slowly and were observed only at some particular area. Time-resolved static light scattering measurements revealed that the transformation from ACP to HAP was inhibited when free phosvitin was present in the calcium phosphate solutions. The transformation kinetics in the absence of phosvitin, which is a direct reconstruction of the inner ACP structure to HAP, was changed to heterogeneous growth of HAP on ACP with time.     

The seeded growth of calcium phosphates. Surface characterization and the effect of seed material

The kinetics of growth of calcium phosphate on seed materials hydroxyapatite, “amorphous” calcium phosphate, enamel, and dentine has been studied at 25°C and at constant physiological pH in stable supersaturated solutions of calcium phosphate. The grown material was characterized chemically, by x-ray powder diffraction and specific surface area measurements and by scanning electron microscopy. In addition, dissolution kinetic studies have been made of the material grown at different times in the crystal growth experiments and of “amorphous” calcium phosphate. The crystallization experiments were made over a range of initial supersaturation to obtain information about the nature of the calcium phosphate phases formed. The specific surface area of the grown phases show marked changes during the growth experiments. The results of the dissolution experiments indicate that the solid material formed in the early stages of crystallization has a stoichiometry corresponding to OCP.     

Direct growth of aligned multiwalled carbon nanotubes on treated stainless steel substrates

Growth of aligned carbon nanotubes (CNTs) on electrically conductive substrates is promising for many applications; however, the lack of complete understanding of the substrate effects on CNT growth poses a lot of technical challenges. Here, we report the direct growth of aligned multiwalled nanotubes (MWNTs) on chemically treated stainless steel (Type 304) using a chemical vapor deposition (CVD) process. A detailed X-ray photoelectron spectroscopy (XPS) analysis has been carried out for the various treated samples in order to better understand the correlation between the surface properties of the substrates and the MWNT growth. The XPS studies revealed that the CNTs prefer to grow on the enriched surface of iron oxides obtained by the chemical treatment rather than on the passive chromium oxide films present on the surface of the as-received stainless steel substrates. The density and alignment of the MWNTs could therefore be controlled by tuning the ratio of the iron oxides to chromium oxides through the chemical treatment on the stainless steel surfaces. On the basis of this method, selective growth of CNT patterns on stainless steel has also been demonstrated.     

Stainless steel electrospray probe: a dead end for phosphorylated organic compounds?

A study of the interaction of phosphorylated organic compounds with the stainless components of a liquid chromatography-electrospray ionisation-mass spectrometry system (LC-ESI-MS) was carried out to disclose a (forgotten?) likely pitfall in the LC-ESI-MS analysis of phosphorylated compounds. The retention behaviour of some representative compounds of different important classes of phosphorylated biomolecules such as nucleotides, oligonucleotides, phosphopeptides, phospholipids and phosphorylated sugars was investigated during their passage through the injector and the stainless steel electrospray capillary. It became clear that the stainless steel components within the LC-ESI-MS setup were able to retain and trap phosphorylated compounds when these compounds were introduced under acidic conditions (0.1% acetic acid). Their release from these stainless steel parts was accomplished by applying an extreme basic mobile phase (25-50% ammonium hydroxide, ca. pH 12). From the data collected one could conclude that the availability of a primary phosphate group appeared imperative but was not always sufficient to realise adsorption on a stainless surface. Furthermore, the number of phosphate moieties seemed to enhance the adsorption properties of the molecules and hence roughly correlated with the analyte fraction lost. Corrosion of the inner surface caused by the mobile phase and the electrospray process was found to be an important factor in the course of these adsorption phenomena.     

医用CVIC/C复合材料表面仿生沉积生物活性钙磷涂层

为了在医用化学气相渗透工艺(CVI)C/C复合材料表面制备生物活性钙磷涂层,用阴极声电化学工艺处理CVIC/C复合材料,再将试样浸泡于过饱和钙磷溶液中,使其诱导钙磷晶体生长.XPS研究表明,经声电工艺处理后,CVIC/C复合材料表面发生了改性;SEM,XRD和FTIR研究表明,在过饱和钙磷溶液中,未经声电化学处理的CVIC/C复合材料不具有诱导钙磷晶体生长的功能,而改性的CVIC/C表面能够诱导钙磷晶体生长,形成片状五水磷酸八钙(OCP)涂层.同时讨论了OCP沉积的形成机理.     

磷酸镧和二烷基二硫代磷酸锌及其复合添加剂对通用锂基脂摩擦学性能的影响

合成了稀土化合物磷酸镧，利用四球摩擦磨损试验机考察了磷酸镧，商品添加剂二烷基二硫代磷酸锌及两者的复合添加剂对通用锂基脂摩擦学行为的影响，用扫描电子显微镜和X射线光电子能谱仪（XPS）观察分析了钢球磨损表面形貌及其元素的化学状态。研究结果表明：磷酸镧和二烷基二硫代磷酸锌均可增加通用锂基脂的承载能力，磷酸镧可提高锂基脂的减摩抗磨能力，二烷基二硫代磷酸锌对基础脂的减摩抗磨性能的作用效果不稳定。含上述添加剂的锂基脂在摩擦副表面发生化学吸附或摩擦化学反应，生成由锂基脂和添加剂共同作用形成的边界润滑膜，从而改善锂基脂的润滑性能。     

Oberfl?chenuntersuchungen zur Phosphatisierung von unlegierten Stahlblechen

Zusammenfassung Unterschiedliche Ergebnisse im Korrosionsverhalten von zwei unlegierten, phosphatierten Feinblechsorten mit Farbauftrag wurden auf die Korngrößendifferenz der Phosphatdeckschicht zurückgeführt. Zur Klärung des Keimbildungs und Wachstumsverhaltens der Phosphatkristalle wurden chemische Analysen im Oberflächenbereich der Walzproben mit der Ionenmikrosonde vorgenommen. Die Ausbildung einer Adsorptionsschicht mit hohen Kohlenstoffanteilen konnte mit durch den Walzvorgang hervorgerufenen Konzentrationsänderungen der Eisenbegleitelemente in m-tiefen Oberflächenschichten in Zusammenhang gebracht und deren Einfluß diskutiert werden.

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Surface examinations for the phosphatization of non-alloyed steel sheets

Summary Differences in the results of corrosion tests of two non-alloyed phosphatized and painted steel sheets were related to differences in the grain sizes of their phosphate coating. Chemical analysis in the surface region of the rolled steel samples was made by an Ion Microprobe to determine nucleation and growth of the phosphate crystals. The formation of an adsorption layer with high carbon content could be related to the concentration changes of the non-alloyed elements in m-deep surface layers; this relationship is discussed.

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Wir danken dem Conselho National de Desenvolvimento Científico e Tecnológico (CNPq) für finanzielle Unterstützung.     

The influence of surface modification of lithium zinc phosphate pigment on corrosion inhibition of mild steel and adhesion strength of epoxy coating

In this paper, the influence of sol–gel surface modification of lithium zinc phosphate (LZP) pigment by methacryloxy propyl trimethoxy silane on corrosion inhibition, dispersion stability and adhesion strength was studied. IR spectroscopy and thermogravimetric analysis confirmed that organic functional group was successfully grafted onto the LZP surface. EIS and polarization measurements of mild steel showed an improvement in corrosion resistance for the extract of surface modified pigment in 3.5 % NaCl solution which was connected to better solubility proved by ICP-OES. The dispersion stability of the pigment in epoxy resin was found to be improved after surface modification. In addition, the adhesion strength of the epoxy coating containing surface modified pigment to mild steel after exposure to salt spray (5 % NaCl solution) was enhanced. The sol–gel surface modification had led to increase in hydrophobicity of the pigment particle surface, but simultaneously increased solubility of the pigment in water possibly due to the lower degree of agglomerates or aggregates of the pigment particles.     

A severe peak tailing of phosphate compounds caused by interaction with stainless steel used for liquid chromatography and electrospray mass spectrometry

A severe peak tailing was observed for adenosine 5'-monophosphate in flow injection analysis with stainless steel tubing and water/methanol mixture (1:1, v/v) as carrier. The cause of the peak tailing was investigated by focusing on the chemical structure of the analytes, the material used for the analytical systems and the composition of the carrier. We clarified that the peak tailing was caused by the interaction between phosphate residues in the analytes and stainless steel. The severe peak tailing did not occur with stainless steel tubing when the phosphate compounds were analyzed with carrier containing phosphoric acid or phosphate buffer. The findings indicate that such ill peak profiles are usually not considerable in conventional HPLC separation because phosphoric acid or phosphate buffer is quite commonly used in eluents. In LC-MS, however, the use of phosphoric acid and phosphate buffer is usually avoided because of their non-volatility; therefore this interaction between stainless steel and phosphate compound becomes predominant and results in severe peak tailings. We also found an effective method for avoiding the interaction. When stainless parts, such as LC tubing and ESI spray capillary, were treated with phosphoric acid prior to analysis, the peak profiles of the phosphate compounds were dramatically improved, even when non-phosphate buffer is used as carrier.     

Different techniques for determining the coating weight of phosphate layers on galvanized steel by means of FT-IR-spectrometry

The determination of the weight per unit area (“coating weight”) of phosphate layers on galvanized steel by means of FT-IR-spectrometry has been performed by three different techniques: (i) principal component regression (PCR) of absorption data, (ii) utilizing the thickness dependent wavenumber shift of a band due to a special optical surface effect observed with parallel-polarized radiation and (iii) of an interference band observed with perpendicular-polarized radiation.     

On the kinetics of apatite growth on substrates under physiological conditions

Derived from reaction kinetics, a simple but useful method, based on "apatite forming capacity" or AFC of solutions mimicking blood plasma, is proposed to decipher the rate of calcium phosphate mineralization. Apatite growth rate constants were calculated using this method for a model composite surface varying the volume fraction of synthetic hydroxyapatite (HA) in a polymer matrix. Previously reported data for mineralized surfaces on Ta, Ti, and its alloys are also analyzed similarly and compared. Utilizing the growth rate constant, the bioactivity of the materials was indexed in vitro. Complementarily, semiempirical quantum mechanical calculation (ZINDO method) showed that the interaction of cations with TRIS-hydroxymethyl aminomethane molecules in the solution is stronger than that with the polymer substrate considered, but weaker than hydrated Ti and TiO(2) surfaces. This analysis then quantifies for example the extent of polymer inertness and the "bioactivity" of alkali treated Ti. The growth rate constants for the model materials prepared in this work are explained on the basis of localized dissolution of HA, the amount of which simply increases with increasing volume fraction of HA in the composite.     

Quantitative prediction of the reduction of corrosion inhibitor effectiveness due to parasitic adsorption onto a competitor surface

We have investigated how the effectiveness of a corrosion inhibitor added to an aqueous solution to suppress the corrosion rate of steel is reduced by the addition of sand. The equilibrium adsorption isotherms of the inhibitor with respect to both the steel surface (consisting of iron carbonate under the corrosion conditions used here) and the sand surface have been measured. The results enable the quantitative calculation of how the surface concentration of inhibitor at the steel surface is reduced by sand addition. Combining the adsorption information with measurements of how the steel corrosion rate depends on the inhibitor surface concentration enables the quantitative prediction of the inhibitor effectiveness as a function of sand concentration. Excellent agreement is obtained between calculated and measured values of the inhibitor performance as functions of both inhibitor and sand concentrations. This methodology demonstrates how the optimization of a corrosion inhibitor formulation for specific application conditions should take into account the parasitic adsorption of the inhibitor onto the competitor surfaces present.     

A new Phosphorylated Polysaccharide for Biomedical Applications: Generation of 3D Scaffolds with Osteogenic Activity and Coating of Titanium Oxide Surfaces

Summary: A new phosphorylated derivative of carboxymethylcellulose and amidic carboxymethylcellulose containing one phosphate group for each disaccharide unit was synthesized using sodium trimetaphospahte (STMP) as the phosphating agent. The new polysaccharide was characterized by infrared spectroscopy (FT-IR) and the amount of phosphate groups was determined by elemental analysis. These modified polysaccharides were used both to prepare 3D scaffolds and functionalize titanium oxide surfaces with the aim to improve the osseointegration with the host tissue. The presence of phosphate groups modify the physical-chemical properties of the hydrogels with respect to the native ones. The evaluation of the bioactivity of the phosphorylated carboxymethylcellulose hydrogels towards osteoblast-like cells showed a significant increase in the osteocalcin production. The modified surfaces were chemically characterized by means of X-ray photoelectron spectroscopy (XPS) and FT-IR, whereas the surface topography was analysed by Atomic Force Measurements (AFM) measurements before and after the polysaccharide coating. In vitro biological tests using osteoblast-like cells demonstrated that phosphorylated carboxymethylcellulose functionalized TiO₂ surfaces promoted better cell adhesion and significantly enhanced their proliferation. These findings suggest that the phosphate polysaccharide both as a 3D scaffold and as a surface coating promotes osteoblast growth potentially improving the biomaterial osseointegration rate.