Electrochemical study of protective behavior of organic coating pigmented with zinc aluminum polyphosphate as a modified zinc phosphate at different pigment volume concentrations

Electrochemical impedance spectroscopy was employed to evaluate protective performance of the solvent-borne epoxy coatings pigmented with zinc aluminum polyphosphate as a representative of phosphate-based anticorrosion compounds at different Lambda values. Furthermore, the effective ratio of the pigment volume concentration (PVC) to the critical pigment volume concentration (CPVC) was determined. To compare the function of zinc aluminum polyphosphate and zinc phosphate incorporated into coatings, electrochemical noise method as well as electrochemical impedance spectroscopy was taken into consideration. The trend and magnitude of charge transfer, coating and noise resistances plus the amplitude of the current noise fluctuation indicated superiority of the modified pigment. In order to provide an insight into the mechanism by which anticorrosion pigments improve protective behavior of coating, performance of bare metals exposed to pigment extracts was assessed through taking advantage of electrochemical impedance spectroscopy and electrochemical noise method as well.     

Cathodic disbondment of epoxy coating with zinc aluminum polyphosphate as a modified zinc phosphate anticorrosion pigment

As an approach to improve the resistance of protective coatings to the disbondment, modification of the formulation through incorporation of zinc aluminum polyphosphate anticorrosion pigment representing third generation phosphates was examined in this paper. The data obtained from cathodic disbonding test, electrochemical impedance spectroscopy and pull-off indicated that introduction of zinc aluminum polyphosphate within epoxy coating could provide improved resistance to cathodic disbonding as well as superior adhesion strength. The superiority in the presence of the modified pigment was connected to deposition of a layer at the disbonding front and locally controlled pH as well. The precipitation restricting active zone available for electrochemical reaction was confirmed by SEM.     

Evaluation of anti-corrosive pigments by pigment extract studies, atmospheric exposure and electrochemical impedance spectroscopy

The inhibition efficiencies of zinc chromate, barium metaborate, calcium silicate, amino carboxylate, calcium barium phosphosilicate, aluminum triphosphate and a modified zinc phosphate on the corrosion of steel and zinc were determined by polarization experiments on pigment extracts. Zinc phosphate and zinc chromate were the best and were studied further to determine the effect of pH and chloride concentration on their inhibition of steel. Zinc chromate is adversely affected by high concentration of chloride ions, which effect seems to be less pronounced on zinc. A low pH, although increasing the solubility of zinc phosphate, does not increase its efficiency. The pigments were also incorporated into an epoxy-poly(amide) binder, applied to cold-rolled steel and galvanized steel, exposed at a marine exposure station and the degradation monitored by electrochemical impedance spectroscopy. There was a general correlation between the results of pigment extract studies and atmospheric exposure except in the case of phosphate pigments on cold rolled steel.     

A new pigment for smart anticorrosive coatings

The purpose of this paper was to evaluate the performance of a modified zeolite as an anticorrosive pigment for paints. A procedure to prepare the pigment was outlined and its anticorrosive properties assessed following the electrochemical behavior of a steel electrode in pigment suspension. In a second stage, alkyd paints were formulated employing different anticorrosive pigments: (1) 30% by volume (v/v) of the modified zeolitic rock, (2) 10% (v/v) of zinc phosphate, and (3) a mixture of 10% (v/v) zinc phosphate plus 20% (v/v) of the modified zeolitic rock. In every case, percentages were referred to the total pigment content. Titanium dioxide, zinc oxide, and barium sulfate were incorporated to complete the pigment formula. The pigment volume concentration/critical pigment volume concentration (PVC/CPVC) ratio was 0.8. The performance of the resulting anticorrosive paints was assessed by accelerated (salt spray and humidity chambers) tests and electrochemical (corrosion potential, ionic resistance, and polarization resistance) essays. It was demonstrated that the modified zeolite is effective in protecting steel from corrosion when it is used in combination with zinc phosphate. There exists a synergism between the modified zeolite and zinc phosphate that allows the zinc phosphate content in anticorrosive paints to be reduced.     

三聚磷酸铝防锈颜料在涂料工业中的应用

本文阐述ＡＰＷ了防锈颜料的特性及其在各种溶剂型涂料、水溶性树脂涂料以及厚浆型防腐涂料等方面的应用情况，表明ＡＰＷ颜料比红丹、锌铬黄。磷酸锌等防锈颜料具有更优越的性能，是一种值得推广的新型无毒防锈颜料。     

Anticorrosive polyurethane paints with nano- and microsized phosphates

Two types of phosphate fillers (nanosized aluminum phosphate and microsized aluminum–zinc phosphate) were tested as anticorrosive fillers in 2 K solvent-borne polyurethane paints based on commercial acrylic resin with OH groups and an isophorone diisocyanate-type hardener. Three coating compositions containing commercial fillers (mica/quartz, TiO₂, wollastonite, talc) and also mentioned nanosized aluminum phosphate or microsized aluminum–zinc phosphate were prepared using a pearl-mill as well as a laboratory dissolver, applied onto a steel substrate and cured at room temperature for 14 days. An influence of the type and content of a phosphate filler on properties of polyurethane paints and coatings has been investigated. Incorporation of nanosized aluminum phosphate into coating compositions increases their viscosity while cured paints exhibit reduced adhesion to steel substrates. The results of corrosion tests in a salts spray chamber as well as immersion in an aqueous NaCl solution indicated that the paint system with 9.8 wt.% of applied nanofiller had similar protective properties to a polyurethane coat containing a higher dose (i.e. 15.6 wt.%) of commercial microsized aluminum–zinc phosphate.     

Optimization of potassium zinc phosphate anticorrosion pigment by Taguchi experimental design

The synthesis condition of potassium zinc phosphate pigment was optimized with respect to corrosion inhibition in extract solution and dispersion stability in an epoxy resin by application of Taguchi experimental design. Processing parameters, including calcinations time, quiescent time, mixing rate and KOH/ZnCl₂ mole ratio are selected as the influential parameters. Corrosion inhibition of the pigments in the extract solutions and dispersion stability in the epoxy resin were evaluated by electrochemical impedance spectroscopy (EIS) and turbidity measurement, respectively. The pigment synthesized under optimal condition was characterized by XRD, which showed formation of KZnPO₄ and KZn₂PO₄(HPO₄). Corrosion protection of the epoxy coating containing synthesized pigment at optimal condition was evaluated by salt spray and compared to the unpigmented epoxy coating. Salt spray results showed higher corrosion protection of the epoxy coating in the presence of potassium zinc phosphate, which could be attributed to lower diffusivity of the pigmented coating to Cl⁻ or formation of phosphate layer confirmed by SEM–EDX.     

Electrochemical examining behavior of epoxy coating incorporating zinc-free phosphate-based anticorrosion pigment

Protective performance of the epoxy primer containing strontium aluminum polyphosphate (SAPP) as a zinc-free phosphate-based anticorrosion pigment is aimed to assess in this work through taking advantage of electrochemical impedance spectroscopy (EIS) and electrochemical noise method (ENM). The absence of zinc offers an excellent environmentally friendly profile to the class of inhibiting compound. In the pigment extracts, the electrochemical techniques revealed superiority of SAPP compared to the conventional zinc phosphate (ZP). The behavior was connected to precipitation of a protective layer on the surface exposed to SAPP. In comparison with ZP, the most effective SAPP content in the protective primer was then determined using EIS.     

铝合金磷化膜性能的研究

采用中温锌系磷化工艺对LY12硬铝合金进行磷化处理获得磷化膜.通过硫酸铜点滴试验,电化学测试等考查了磷化膜的耐蚀性;利用扫描电子显微镜、能谱仪等对磷化膜的表面形貌、化学成分进行分析.结果表明,该磷化膜外观颜色呈浅灰色,均匀光亮,耐蚀性好,硫酸铜试验耐蚀t为63 s,线性极化电阻为4.174 kΩ;表面形貌为片状晶体层层...     

集装箱用水性聚氨酯外面漆的研制

以物理性能优异的水性聚氨酯树脂为主要成膜物质,并利用防腐性能优异的苯丙乳液对其进行共混改性,优选了无毒防锈颜料,制备出了一种综合性能优异的集装箱专用水性聚氨酯外面漆。结果表明:当丙烯酸树脂B的混入量为20%,以磷酸锌为防锈颜料,颜填料体积浓度(PVC)为25%时,外面漆的性能满足JH/T E01—2008集装箱涂料行业标准。并系统地考察了外面漆施工时易出现的流挂、针孔等漆膜弊病的影响因素及防治措施。     

The effects of zinc aluminum phosphate (ZPA) and zinc aluminum polyphosphate (ZAPP) mixtures on corrosion inhibition performance of epoxy/polyamide coating

The epoxy/polyamide coating was loaded with different pigment mixtures of the zinc phosphate (ZP), zinc aluminum phosphate (ZPA) and zinc aluminum polyphosphate (ZAPP) pigments. The electrochemical impedance spectroscopy (EIS) and salt spray test were used to investigate corrosion inhibition performance of the coatings. The adhesion strengths of the coatings were measured by a pull-off test. Results revealed lower coating pull-off strength loss when the ZPA and ZAPP pigments were used. A significant decrease in number of blisters together with low pull-off strength loss and best corrosion inhibition properties were observed when the mixture of 80:20 of ZAPP:ZPA was used.     

Corrosion inhibition of aluminum by organic coatings formulated with calcium exchange silica pigment

One of the first commercial ion-exchange anticorrosive pigments to be developed was Shieldex^® (Si/Ca). Its proposed corrosion protection mechanism, based on the retention of aggressive cations and the subsequent release of calcium cations, has created certain controversy. A number of studies have focused on the anticorrosive behavior of this pigment on carbon steel and galvanized steel to replace chromates (Cr⁶⁺) as inhibitor pigment, but none has considered its performance on aluminum or aluminum alloys. In this research, alkyd coatings have been formulated with Si/Ca pigment at different concentrations and applied on aluminum 1050 (Al 99.5%) specimens. These specimens have then been subjected to accelerated tests (condensing humidity, salt spray, and Kesternich) and natural weathering in atmospheres of different aggressivity. Corrosion performance has been also evaluated in the laboratory by electrochemical impedance spectroscopy. The study has also considered an organic coating with zinc chromate anticorrosive pigment for comparative purposes. The results obtained with organic coatings formulated with Si/Ca pigments confirm that they provide corrosion protection of the underlying aluminum substrate, even improving the behavior of the reference zinc chromate in some environmental conditions.     

Methodology for zinc phosphate pigment incorporation into polypyrrole matrix

In this work, the incorporation of a commercial zinc phosphate pigment into polypyrrole (PPy) matrix during its electrochemical synthesis on mild steel was studied in order to produce PPy/zinc phosphate composite films as a protective layer against corrosion. Potassium nitrate, oxalic acid, tosylic acid and sodium salicylate solutions were used as electrolytes in cyclic voltammetry and galvanostatic polarisation studies. The influence of synthesis parameters such as nature, concentration, pH and stirring of the electrolyte on the degree of incorporation of the pigment was investigated, as well as time and current densities of the electropolymerisation process. Their influence on current efficiency was also evaluated. Sodium salicylate was the only electrolyte to show a high current efficiency in the polymerisation reaction and to yield a composite film with a reasonable amount of zinc phosphate. In this electrolyte medium, X-ray photoelectron spectroscopy (XPS) analysis showed that zinc phosphate may be found in the polymeric matrix: (i) as a conductive ionic minority form and (ii) as a non-conductive non-ionic majority one for higher incorporation levels. Scanning electron microscopy (SEM) showed that zinc phosphate is heterogeneously distributed on the surface of the polymer.     

磷酸铝包覆氧化铁黄颜料的制备及其耐温性能研究

氧化铁黄颜料受热易脱水变色,限制了其在温度较高环境下的应用。提高氧化铁黄的热稳定性具有很重要的意义。通过液相水解沉积的方法对氧化铁黄表面进行磷酸铝表面包覆,研究了磷酸铝包膜的工艺条件（pH、包膜量、温度）对氧化铁黄包覆的表面形貌和微观结构的影响。结果表明：在pH为7、磷酸铝的包膜量为13%、包覆温度为65 ℃时,在氧化铁黄表面的包覆效果最佳。采用色差法研究了在最佳条件下进行磷酸铝包覆的氧化铁黄颜料,结果表明其耐温性得到显著提高。     

Electrochemical assessing corrosion inhibiting effects of zinc aluminum polyphosphate (ZAPP) as a modified zinc phosphate pigment

Undesirable anti-corrosion performance of zinc phosphate pigment, the classical chromate replacement, has led researchers to take modification into account. Polyphosphate-based anti-corrosion pigments as a result of modification of zinc orthophosphate have been found to function much more efficiently. This study aimed to evaluate performance of steel samples immersed in 3.5% NaCl aqueous solution-containing zinc aluminum polyphosphate (ZAPP) pigment extract compared to those involving conventional zinc phosphate (ZP) pigment extract and also no pigment (blank) using electrochemical tests such as electrochemical impedance spectroscopy (EIS) and linear polarization (LP) as well as surface analysis. Impedance spectra and polarization curves revealed two different trends, showing the superiority of ZAPP pigment. Based on the results of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), presence of a precipitated layer on the surface was confirmed when steel sample was immersed into the solution-containing ZAPP.     

磷酸锌/云铁灰环氧涂层防腐性能的研究

选用磷酸锌为主要防锈颜料,协同云母氧化铁灰,制备无溶剂型环氧防腐涂料.考察涂层的基本性能,并采用交流阻抗(EIS)测试技术,分析了颜料体积浓度(PVC)、活性稀释剂和防锈颜料质量比对涂层防腐性能的影响.实验结果表明:该涂料固含量高达98%以上,是环境友好型涂料;PVC小于12%时,涂层具有较好的防腐性能;PVC为8%,活性稀释剂添加量为2%,云铁灰与磷酸锌质量比为1:4时涂层的防腐性能最佳.在涂层浸泡一定时间后,磷酸锌能防止腐蚀的进一步发生,起到有效抑制腐蚀的作用.     

Comparison of the efficiency of inorganic nonmetal pigments with zinc powder in anticorrosion paints

This paper deals with the study of properties of anticorrosion pigments of varying chemical composition in epoxyester paints. Two type lines of paints were prepared. The first line comprised an anticorrosion pigment with a PVC concentration of 10% while the other line comprised an anticorrosion pigment with a PVC concentration = CPVC. The following nontoxic anticorrosion pigments were observed: zinc phosphate, zinc phosphomolybdate, calcium hydrogen phosphate, zinc phosphate modified with an organic corrosion inhibitor, strontium–aluminum polyphosphosilicate, zinc–aluminum polyphosphate, calcium metaborate, calcium ferrite, calcium borosolicate, and strontium chromate. The epoxyester primers were observed for the effect of the type of pigment on the anticorrosion properties. Anticorrosion efficiency was derived from tests in a condenser chamber and in a salt spray cabinet as well as from a test of chemical resistance of pigmented coatings. The evaluation of anticorrosion efficiency of inorganic nonmetal pigments was carried out by means of comparison with anticorrosion efficiency of metal dust.     

高性能防锈颜料磷酸锌的研制

采用液-液直接法,利用氧化锌和磷酸来生产磷酸锌。通过控制氧化锌悬浮液的加料速度、分散剂的用量、复合表面改性剂的用量,用吸油量、磷酸锌含量、粒度分布和耐盐雾性能来表征磷酸锌防锈颜料的最佳制备工艺。     

Stabilization of aluminum pigment in waterborne paints

The corrosion of aluminum pigments in aqueous alkaline paint media, which results in the evolution of hydrgen, can be inhibited by certain substances. The combination of noninhibiting paint resins with three corrosion inhibitors (salicylic acid, a fluorinated phosphate surfactant, and an epoxy ester resin) has been studied. The presence of the resins does not significantly affect the stabilization of the aluminum pigment at pH 10 by the corrosion inhibitors. With the addition of corrosion inhibitors, the hydrogen volume evolved from aqueous aluminum pigment dispersions is surprisingly reduced by stirring. However, when heated to +40°C aqueous aluminum pigment dispersions with inhibitors evolve more hydrogen; at pH 8 the results are still satisfactory even at +40°C.     

Studying the corrosion protection properties of an epoxy coating containing different mixtures of strontium aluminum polyphosphate (SAPP) and zinc aluminum phosphate (ZPA) pigments

Epoxy/polyamide coatings were loaded with different mixtures of strontium aluminum polyphosphate (SAPP) and zinc aluminum phosphate (ZPA) pigments. Moreover, a coating containing zinc phosphate (ZP) was prepared as a reference sample. The coatings were applied on St-37 steel substrates and then were exposed to 3.5 wt% NaCl solution up to 35 days. The corrosion inhibition properties of the pigments extracts were studied on bare steel samples by a potentiodynamic polarization technique after 24 h immersion. The morphological properties and corrosion resistance of the coatings were investigated by scanning electron microscope (SEM), optical microscope, electrochemical impedance spectroscopy (EIS) and salt spray tests.