Anticorrosive behaviour of alkyd paints formulated with ion-exchange pigments

Hexavalent chromium compounds (chromates) have been widely used as inhibitive pigments in the formulation of anticorrosive paints. However, their high toxicity and carcinogenic effects are forcing the development of effective chromate-free organic coatings. One such alternative, which is very attractive from a scientific point of view, is the use of ion-exchangeable pigments (IEPs).

The few studies conducted with this type of pigment are not conclusive about their anticorrosive efficiency and controversy surrounds their functioning mechanisms, interchange capacity and anticorrosive performance.

In the present research, which focuses on the anticorrosive protection of this type of pigment, alkyd paint coatings formulated with vanadate-hydrotalcite (HT/V) (anionic) and calcium/silica (Ca/Si) (cationic) IEPs have been applied on low carbon steel specimens. A traditional zinc chromate pigment has also been used for comparative purposes.

The effect of these non-toxic pigments on the protective properties of coatings has been tested by means of natural and accelerated corrosion tests (humidity, salt spray and Kesternich, 0.2 l SO₂) and electrochemical impedance spectroscopy (EIS).

None of the IEPs equalled the anticorrosive behaviour of the zinc chromate in the different tests. The anionic pigment (HT/V) seems to present good behaviour in chloride environments (salt spray, NaCl solutions, etc.) while the cationic pigment (Ca/Si) performs well in the humidity condensation and SO₂ tests.     

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.     

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.     

碳纳米管对水性环氧富锌防腐涂料防腐性能的影响

将碳纳米管（ CNTs）以水性浆料的形式添加在环氧乳液中,制备 CNTs改性水性环氧富锌防腐涂料以解决传统富锌涂料高锌含量的问题。通过 SEM来观察涂层的形貌,附着力、耐冲击测试表征涂层的机械性能,开路电压、极化曲线和耐盐雾等方法探讨碳纳米管含量对环氧富锌防腐涂层防腐性能的影响。结果表明：涂层中添加 CNTs可以增强涂层的耐冲击性,且 CNTs对涂层附着力的影响不显著;涂层防腐性能随 CNTs含量的增加呈现先增强后减弱的趋势;在 60.0%锌含量体系中,添加 0.2%含量的 CNTs,与 60.0%锌含量空白组比较,涂层腐蚀电流密度降低 66.7%,与 70.0%锌含量空白组比较,其腐蚀电流密度也可降低 53.8%,且耐盐雾实验 2 000 h后,涂层仍未出现明显腐蚀现象,即在60.0%锌含量体系中添加 0.2%含量的 CNTs,不仅可以降低涂层 10.0%的锌含量,还可以增强涂层的防腐性能。     

咪唑啉季铵盐缓蚀剂改性蒙脱土/水性环氧纳米复合涂料

以油酸、二乙烯三胺和氯化苄为原料,合成了油酸基咪唑啉季铵盐缓蚀剂。通过FTIR、¹HNMR对其结构进行了表征,并离子交换至钠基蒙脱土(DK0)层间,制备了缓蚀剂改性蒙脱土(QACDK0)。通过XRD、TGA和UV-Vis对其结构、组成及层间缓蚀剂释放性能进行了表征。结果表明,咪唑啉季铵盐缓蚀剂约占QACDK0质量的38.96%,并将蒙脱土层间距由1.28 nm(DK0)扩大至3.98 nm(QACDK0)。利用DLS及Zeta电位对添加有QACDK0的水性环氧树脂进行了稳定性测试,其Zeta电位为–27.8 m V,具有较高的稳定性。电化学阻抗谱(EIS)测试表明,在腐蚀介质中浸泡30 d后,基于QACDK0制备的清漆漆膜仍具有2.29×10⁸?·cm²的高阻抗,表明涂层具有较好的耐腐蚀性。并且在耐中性盐雾测试中,QACDK0对应的防腐色漆耐盐雾时间最长,验证了该涂层具有良好的耐盐雾性能。     

High performance water-based paints with non-toxic anticorrosive pigments

Legal restrictions have impelled the replacement of solvent-borne resins and of toxic chromates and lead-bearing pigments in the elaboration of paints. Water-based anticorrosive paints have come a long way to improve their efficiency but their behaviour is said to be poorer than that of solvent-based paints. Nevertheless, recent advances in water-borne technologies have now resulted in improved resin systems that may be employed to produce heavy-duty coatings.

The objective of this paper is to formulate high performance water-borne paints pigmented with non-toxic phosphate inhibitors. The anticorrosive properties of the paints were evaluated by accelerated tests (salt spray and humidity cabinets) and electrochemical tests (electrochemical impedance spectroscopy, EIS). The anticorrosive properties of the pigments were also evaluated by electrochemical tests.

It was found that it is possible to formulate high performance anticorrosive paints by selecting adequate water-borne resins and ecological pigments.     

家电预涂卷材底漆防腐性能的影响因素

通过中性盐雾试验研究了家电预涂卷材底漆防腐性能的一些主要影响因素,包括基板、预处理、树脂(交联树脂和环氧树脂)和颜填料对防腐性能的影响。     

Mechanisms of non-toxic anticorrosive pigments in organic waterborne coatings

Investigations have been carried out concerning the mechanism of the behaviour of non-toxic anticorrosive pigments belonging to the group of phosphates, ferrites and ion exchange pigments in waterborne systems. The mechanism controlling the protective effectiveness of organic coatings is complex and results from simultaneous activity of various agents, from among which the kind of the corrosion inhibitor and the structure of the coating are of fundamental importance. The effect of pigments on the protective properties of coatings was tested by means of electrochemical impedance spectroscopy (EIS), scanning vibrating electrode technique (SVET) as well as the salt spray and Prohesion tests. For the investigation of the structure of coatings the porosymetric method and modulated-force thermomechanical analysis (mf TMA) were applied. The results of these investigations have shown that calcium zinc phosphate and zinc ferrite are the most effective. These pigments take part in the passivation of steel, which has been proved by the results of electrochemical investigations and by the presence of the passive layers as has been found out by X-ray diffraction (XRD), energy dispersive X-ray analysis (EDXA) and scanning electron microscopy (SEM). Calcium zinc phosphate and zinc ferrite affect the structure of the coatings, increasing the glass transition temperature (Tg) of the coatings. Zinc phosphate and calcium-exchanged silica do not act in compliance with electrochemical mechanism neither do they improve the barrier properties of the binder.     

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.     

石墨烯改性环氧锌基防腐涂料的制备与性能研究

针对传统环氧富锌涂料环保性差、质量大、成本高等问题,利用石墨烯优异的导电性与独特的二维片层结构可增强涂层防腐性能的特性,取代传统环氧富锌涂料中的部分锌粉,以期制备低锌含量的石墨烯环氧锌基涂料。首先将石墨烯材料与环氧树脂预混合,掺杂天然高分子表面活性剂,制备一种高分散性石墨烯 /环氧树脂浆料;然后将其与计量的环氧树脂、锌粉、其他功能颜填料复配,通过高速分散与砂磨的制备方式相结合,得到石墨烯改性环氧锌基防腐涂料;最后通过力学性能、连接强度、交流阻抗、耐中性盐雾等方法探索涂层关键性能。研究结果表明：该石墨烯涂层防腐性能优异, 2 000 h盐雾划痕腐蚀扩展 0.9 mm,且力学性能与施工性能好,可广泛应用于船舶、海工设备、桥梁等大型钢结构装备领域。     

Challenges of chromate inhibitor pigments replacement in organic coatings

General considerations concerning pigment grade corrosion inhibitors are presented and new characteristic functional parameters proposed. The chemistry, contemporarily practiced for corrosion inhibitor pigment synthesis, as well as known mechanistic considerations relevant to the corrosion inhibitor species available in pigment grades, are reviewed. Inherent limits of chemistry are outlined regarding the feasibility of developing equally effective and versatile non-toxic alternatives for chromates.

Fundamental aspects of corrosion inhibitor pigment behavior are discussed in the context of organic coatings degradation mechanisms. Disclosed experimental data demonstrate that correlation exists between solubility of corrosion inhibitor pigments, leaching from, and osmotic blistering of organic coatings. A mathematical expression is proposed and empirically proven to adequately describe the leaching rate of corrosion inhibitor pigments from organic coatings.

The barrier function of some high performance organic coatings, such as aircraft or coil, is negligible and requires the contribution of an effective corrosion inhibitor pigment, which, typically, is strontium chromate. In this context, the feasibility of replacing chromate inhibitor pigments is assessed and the “gap” observable between the inhibitor performance of chromates and traditional non-chromate pigments is noted.

Experimental data are displayed regarding the corrosion inhibitor performance of a novel, organic–inorganic, hybrid type corrosion inhibitor pigment in typical aircraft primer application on aluminum and plated steel. The presented data demonstrate the feasibility of chromate replacement in this specific case.     

Enhancing corrosion resistance of aluminum composites in 3.5% NaCl using pigmented epoxy fluoropolymer

The corrosion protection performance of AA6061 T6–10% Al₂O₃ composite, coated with four different fluoropolymer paint systems, were investigated in 3.5% NaCl aqueous solutions under uniform and scratched conditions. A comparison between epoxy-treated clear and pigmented fluoropolymer coatings with newly developed vanadate-based fluoropolymer coatings was performed from corrosion protection, adhesion and durability points of view. The corrosion rates of epoxy-treated clear FLBZ 1074 increased dramatically after less than one month of exposure in 3.5% NaCl aqueous solutions. The addition of iron oxide or titanium oxide as pigments to the fluoropolymer decreased the porosity of epoxy and hence, improved the corrosion resistance. The newly developed vanadate based-clear FLBZ 1074 system showed outstanding corrosion resistance even after two months of immersion in 3.5% NaCl aqueous solutions under scratched coating conditions. The durability of such new coating based on salt spray test results was very promising (>2000 h without any sign of corrosion). The vanadate-pigmented FLBZ 1074 showed a dramatic increase in the corrosion rates. Moreover, the presence of pigments affected negatively the adhesion performance as well as the durability of the coating. A general model has been used to analyze the impedance data in terms of reactions occurring during the interaction of the coated metal with the environment. It was found that the vanadate-treated specimens not only improve the protective power against filiform corrosion as a factor of time, but also maintain the adhesion performance within the acceptable ranges.     

快干单组分含氯防腐涂料的研制

采用磷酸锌、锶铬黄和绢云母作为防锈颜料,选用含氯树脂作为主体树脂,酚醛改性环氧树脂作为辅助树脂,制备了快干单组分含氯防腐涂料。考察了含氯树脂与酚醛改性环氧树脂配比、防锈颜料配比、颜基比以及增塑剂用量等对涂层性能的影响。实验结果表明:该涂料干燥时间≤7 h,为快干型防腐涂料;含氯树脂与酚醛改性环氧树脂质量比为10∶1,磷酸锌加入量为8%、锶铬黄加入量为2%、绢云母加入量为8%、增塑剂加入量为7.4%时,单道涂层的耐盐雾性可达500 h以上。     

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.     

无溶剂重防腐环氧涂料的制备与研究

采用中低相对分子质量树脂体系以及改性脂环胺固化剂,以化学、物理防锈颜料,体质填料为粉料体系制备无溶剂重防腐环氧涂料。通过 EIS、划线盐雾剥离、耐 3. 5% NaCl溶液和 10% NaOH溶液、混合溶液浸泡后的附着力,研究了涂层屏蔽性、耐碱性、湿态附着力。结果表明：铁钛粉、 绢云母粉、长石粉粉料体系涂层屏蔽性、耐碱性最佳;改性脂环胺固化剂屏蔽性好,湿态附着力性能优异;采用 EIS、划线盐雾剥离,耐 3. 5% NaCl溶液、 10% NaOH溶液浸泡以及混合溶液浸泡后附着力下降程度来评价涂层屏蔽性、耐碱性、湿态附着力性能具有一定的可参考性,研究结果与涂层耐阴极剥离实验性能正相关,可用于涂层耐阴极剥离性能的早期评价与判断。     

Comparative electrochemical studies of zinc chromate and zinc phosphate as corrosion inhibitors for zinc

The anticorrosive performance of two inhibitive pigments, zinc chromate and zinc phosphate, was compared using electrochemical impedance spectroscopy (EIS) and the scanning vibrating electrode technique (SVET) in pigment extracts in 0.1 M NaCl. It was observed that zinc was protected from corrosion in both extracts. In tests using hot dip galvanised steel painted with an epoxy primer incorporating the pigments, the SVET detected the anodic and cathodic distribution along the scribes, although no significant differences were observed among the various primers. On the contrary, EIS was able to distinguish processes occurring on the metal surface exposed by the scribe in different samples. For primers with anticorrosive pigment, a time constant at high frequencies was attributed to a layer of protective nature, probably formed by metal ions from the substrate and inhibitive ions leached from the anticorrosive pigments.     

Development of polyorganosilazane–silicone marine coatings

The objective of the present work is the development and characterization of marine coatings based on polyorganosilazanes (PSZ). Two types of coatings containing silicone oils and biocidal compounds were investigated as anticorrosive and antifouling coatings. The flexibility, hydrophobicity and adhesion properties of the PSZ-based coatings on aluminum substrates were studied. Static immersions in natural seawater were investigated to evaluate the antifouling performances of these coatings. The corrosion properties were studied by salt spray tests. Results demonstrated that coatings based on silicone oils appeared to be the most efficient coatings in terms of antifouling and anticorrosive properties. Ten-month antifouling efficiency was revealed for biocide-free polydimethylsiloxane-based PSZ coatings in natural seawater static immersion. The adjunction of dicopper oxide as biocidal pigments was shown to decrease the stability in cans of the corresponding paints and therefore decreasing the flexibility of coatings. In addition, this pigment affected badly the anticorrosive properties of the coatings together with a short antifouling efficiency time. Thus, the silicone oil-based PSZ displayed remarkable advantages in addition to their dual antifouling and anticorrosive properties which are the absence of biocidal compounds released in marine environment and the absence of volatile solvent.     

磷酸锌中重金属对双组分聚氨酯防腐涂料性能的影响

以不同重金属含量的磷酸锌为原料制备双组分聚氨酯防腐涂料,运用傅里叶变换红外光谱仪（FTIR）研究了重金属对双组分聚氨酯防腐涂料固化速率的影响,利用盐雾性能研究了重金属含量对双组分聚氨酯涂料防腐性能的影响。结果表明,磷酸锌中的重金属含量越高,其制备的聚氨酯涂料固化速度越快,耐盐雾性能越差,耐冲击性能越差。     

环保型磷酸盐防锈颜料的研究进展

磷酸盐防锈颜料是当前取代红丹和锌铬黄等传统有毒颜料的有效品种,以其突出的耐腐蚀性能和环保特性在涂料工业中引起重视并取得了长足进展。简要论述无毒磷酸盐防锈颜料的种类,以及国内外应用研究情况,并对其组成、应用性能的发展方向提出了建议。     

Formulation and study of corrosion prevention behavior of epoxy cerium nitrate–montmorillonite nanocomposite coated carbon steel

Nanocomposite coatings which were applied on carbon steel panels based on epoxy cerium nitrate–montmorillonite (MMT) were synthesized and formulated. Nanoparticles were incorporated into epoxy resin by mechanical and sonication processes. The state of dispersion, dissolution, and incorporation were characterized by optical microscopy, sedimentation tests, X-ray diffraction, and transmission electron microscopy. To investigate anticorrosive properties of nanocomposite coatings, electrochemical impedance spectroscopy and salt spray tests were employed. The experimental results showed that epoxy cerium nitrate–MMT nanocomposite coatings were superior to the neat epoxy in corrosion protection effects. In addition, it was observed that the corrosion protection of nanocomposite coatings was improved as the clay loading was increased up to 4–2 wt% cerium nitrate.