管道防腐涂层防腐性能优化研究

随着科学技术的迅猛发展,环氧涂料在管道涂层防腐施工中运用的也越来越频繁,但不能否认的是,虽然防腐技术愈加深化,环氧涂料在使用过程中依然存在着不同程度的起泡。脱落等与管道分离的现象。形成这种现象的原因有很多,例如环氧涂料自身性能方面的缺陷或者阴极保护电位的问题等等因素都可能导致环氧涂料与管道剥离。针对这类问题,本文主要从涂层本身和环境两个方面,对涂层成膜物、阴极保护电位等因素进行研究,分析得出环氧涂层与阴极剥离性能之间的相互作用。     

无溶剂涂料抗阴极剥离性能研究

介绍了无溶剂涂料在石油管道中的应用及其在金属表面产生阴极剥离的机理,分析了无溶剂环氧涂层、无溶剂聚氯酯涂层及无溶剂聚氯酯一环氧涂层抗阴极剥离性能的影响因素。实验表明,涂层的原材料选择、功能性填料的添加及施工工艺等都对抗阴极剥离性能有着显著的影响。     

抗高温阴极剥离防腐环氧粉末涂料的研究

阴极保护和防腐层的联合应用是埋地钢质管道防腐蚀普遍采用的一项技术,已在国内数万公里管道上应用,取得了显著效果。经长期经验积累与技术不断进步,川气东输工程设计对环氧粉末涂层性能指标提出更高的要求,例如:-1.5 V电压下,60℃NaCl溶液浸泡30 d,阴极剥离的剥离半径≤15 mm。通过对阴极剥离对涂层的影响分析,采用自主合成的Amanda1168线形三官能环氧树脂及Amanda999B互穿网络的复合固化剂,辅助纳米硅材料,制成抗高温阴极剥离的粉末涂料,试验结果表明达到川气东输工程技术要求。     

抗阴极剥离环氧涂料的配方设计

介绍了环氧涂料阴极剥离的机理,分析了树脂、固化剂、颜填料和助剂对涂层抗阴极剥离性能的影响,通过对比实验测试,筛选出了合适的树脂、固化剂和颜填料体系,制备了一种具有良好耐阴极剥离性能的环氧涂料,该涂料可广泛应用于港口码头、海上风电、石油平台等领域,具有广阔的应用前景。     

聚脲涂料在长输管道上应用的可能性

对几种管道防腐蚀涂料的技术标准进行了解读和对比,对聚脲和环氧粉末涂层的耐阴极剥离性能进行了展示和比较,提出了环氧粉末涂层作为底层,聚脲涂料作为面层的新的埋地管道涂层结构,并对这种结构的层间附着力,抗阴极剥离性能进行了试验,提出了这种新结构在长输管道上应用的可能性。     

钛合金化学铣切室温固化可剥离性涂料的研制及其性能研究

为使钛合金长时间浸泡在化学铣切加工液中不被漏蚀,实验选用过氯乙烯树脂为主要成膜物、有机硅改性环氧树脂材料和有机包核绿色颜料为次要成膜物、改性硅油和天然抗氧化剂为添加剂,制备了一种室温固化可剥离性涂料,并对其机械性能、可剥离性能、耐盐水浸泡性能进行研究。研究表明,涂料中次要成膜物 I和添加剂 A主要提升涂层的可剥离性,提升涂层强度与韧性;邻苯二甲酸二丁酯能够提高涂料涂层的塑性,降低拉伸强度;苯并三氮和添加剂 B起缓蚀作用;同时添加剂 B能改善涂料流动性,防止涂层老化。研制的涂料可在室温下固化,具有良好的塑性、可剥离性、拉伸强度及耐盐水浸泡性能。     

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。     

耐阴极剥离有机涂层的研究进展

简介了水环境中有机涂层保护、阴极保护及其联合用于金属防护的机理,综述了有机涂层阴极剥离机理,分析了影响有机涂层阴极剥离的因素,综述了耐阴极剥离有机涂层的设计原则,最后指出了耐阴极剥离有机涂层的研究方向。     

海洋石油平台防腐涂料NORSOK M-501认证试验结果分析

按照NORSOK M-501试验标准要求,对自主开发的海洋石油平台大气区和水下区域的防腐涂层体系性能进行了测试,对测试结果和失效原因进行了分析讨论。结果表明:循环老化试验中,涂层湿附着力的降低是引起划线处腐蚀距离扩大和涂层大面积起泡的主要原因,温变、紫外光、干湿交替的试验条件加速了这一过程;富锌底漆没有起到阴极保护、阻止腐蚀蔓延的作用;阴极剥离试验中,金属/涂层界面处的阴极腐蚀产物是导致海水区涂层阴极剥离的主要原因。     

管道阴极保护与外涂层相互影响的研究进展

阴极保护和外涂层是长输管道防腐蚀的必要措施,本文讨论了管道外涂层和阴极保护共存时相互作用、相互影响的因素.首先总结了管道外涂层种类、缺陷和环境对阴极保护电流渗透的影响,其次概述涂层的剥离、缝隙、破损和硫酸盐还原菌对阴极保护性能的影响,然后概括了管道钢阴极保护对涂层结合力、涂层剥离、涂层电阻和应力腐蚀断裂的影响.指出了研...     

飞溅区维保用高固含量环氧涂料的研制

以液体环氧树脂及改性树脂为基料,以改性胺为固化剂,通过选择相应的颜填料,研制了用于飞溅区维保用高固含量环氧涂料。通过对研制的高固含量环氧涂料进行性能测试,结果表明:该产品不但具备飞溅区防腐要求的耐磨性、耐循环老化、耐海水浸泡及抗阴极剥离性能,同时具有优异的耐高湿性、低表面容忍性及可快速浸泡入水中继续固化性能,满足飞溅区的维保防腐需求。     

The effect of benzimidazole and zinc acetylacetonate mixture on cathodic disbonding of epoxy coated mild steel

Electrochemical behavior of mild steel in the presence of zinc acetylacetonate (Zn(acac)₂) and benzimidazole (BIMIDA) was evaluated by electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution and compared to zinc phosphate (ZP) pigment and zinc potassium chromate (ZPC) pigment extracts. Results showed superior performance of Zn(acac)₂ and BIMIDA mixture (ZBM) compared to ZP pigment, while it introduced inferior inhibitive action compared to ZPC pigment. The epoxy coatings were formulated with ZBM as anticorrosive additive, ZP and ZPC pigments. The disbonding rate of coated steel follows the order: Blank > ZP > ZBM > ZPC. EIS results showed a complex film could be formed at the hole area for the coatings formulated with ZP, ZBM and ZPC. It is concluded that the stronger the complex film on the surface, the lesser the cathodic disbonding rate would be.     

Evaluation of thick organic coatings degradation in seawater using cathodic protection and thermally accelerated tests

Organic coatings are often associated with cathodic protection to fight against the corrosion of metallic structures when immersed in seawater. However, cathodic protection leads to the generation of a strong alkalinity at the metal/coating interface, which causes the degradation of the coating. It is then necessary to develop a reliable method to evaluate the compatibility between organic coatings and the application of cathodic protection.

On one hand, cathodic disbonding tests (ASTM G-8 and G-80) can be driven with an artificial defect but this defect is mainly responsible for the electrochemical response. In addition, calcareous deposit rapidly forms onto the defect zone when cathodic protection is applied which can make difficult the evaluation of coating delamination. On the other hand, immersion of defect-free specimens requires very long testing periods (several months or even years) in order to detect the coating degradation.

In this work, an attempt to accelerate the coatings degradation by imposing a high temperature and thermal cycles were made in order to decrease the test-time duration. The influence of the applied cathodic potential was also investigated. The coating degradation was evaluated by EIS, considering the defect-free zone of coatings. It was shown that the coating degradation is faster in the presence of a defect and for high temperature (45 °C). Moreover, thermal cycles allow to greatly accelerate the degradation of defect-free coatings and then to compare the compatibility of both coatings with cathodic protection.     

Effect of zinc-free phosphate-based anticorrosion pigment on the cathodic disbondment of epoxy-polyamide coating

In the field of protective coatings, zinc-free pigments are proposed as promising anticorrosion compounds due to their excellent environmentally-friendly profile. In this paper, cathodic disbonding performance of a solvent-borne epoxy primer incorporating strontium aluminum polyphosphate (SAPP) as a zinc-free phosphate-based anticorrosion pigment was investigated. Regardless of the applied potential, the presence of SAPP in the coating formulation caused slower growth of the delamination area in comparison to ZP. According to the data obtained from EIS and SEM/EDX, this behavior was attributed to locally controlled pH and the precipitated film restricting active zones available for electrochemical reactions.     

Cathodic delamination of seawater-immersed anticorrosive coatings: Mapping of parameters affecting the rate

Cathodic delamination is one of the major modes of failure for organic coatings immersed in seawater and refers to the weakening or loss of adhesion between the coating and the substrate. The diminished adhesion is the result of electrochemical reactions occurring at the coating–steel interface, where solid iron is oxidized to ferrous ions and oxygen is reduced to hydroxyl ions. In this work, the effects of various parameters on cathodic delamination have been investigated. The parameters are: permeability of the coating, concentration of dissolved oxygen and cations, polarization potential, type of binder, degree of curing, and pigment loading, shape and type. The results show that cathodic delamination increases with increasing concentration of cations up to the point where the concentration of dissolved oxygen becomes insufficient to maintain the corrosion rate. The rate of cathodic delamination is inversely proportional to the magnitude of polarization potential when ions can penetrate the coating, while cathodic polarization does not affect cathodic delamination when the ionic transport is restricted to the coating–steel interface. Increasing the pigment loading or partial replacement of spherical pigments with flake-shaped micaceous iron oxide or aluminium pigments reduces the rate of cathodic delamination. Finally, binders with an increasing amount of secondary hydroxyl groups in the polymer backbone reduce the rate of cathodic delamination while increasing the initial molar ratio of amide to epoxide increases cathodic delamination.     

Determination of the oxygen reduction products on ASTM A516 steel during cathodic protection

The electrochemistry of steel in aerobic and anaerobic aqueous alkaline solutions was studied with or without forced convection to investigate the cathodic processes occurring on steel exposed by defects in polymer coated steel pipe. The results are relevant to the mechanistic understanding of the effect of cathodic protection on the disbonding of fusion bonded epoxy (FBE) coatings on steel. Moderate (pH9.8) and strongly (pH14) alkaline aqueous solutions were used to simulate the water layers at the cathodically polarized steel surface on the soil-side of buried pipe. A rotating gold ring and steel disc electrode (RRDE) in alkaline aqueous electrolyte equilibrated with 1atm oxygen over solution was used to measure the rotation rate dependent current for the electroreduction of oxygen, O2, on an ASTM A516 steel disc and the resulting peroxide generation, which was determined by monitoring the oxidation current on the gold ring. An appreciable fraction of the oxygen reduction current on the steel disk gave rise to peroxide generation over a wide range of potentials, from –0.2 to –0.9V vs SCE in 1M KOH. The observation of peroxide generation is noteworthy, because oxidizing agents, such as peroxide and its decomposition products, superoxide and hydroxy radical, can degrade the polymers used for coating pipelines. As result, oxidative degradation of polymer or interfacial compounds may be a cause of the accelerated disbonding observed for protective coatings on steel pipelines under cathodic protection.     

The impact of pigment volume concentration on the protective performance of polyurethane coating with second generation of phosphate based anticorrosion pigment

In this study the effect of conventional zinc phosphate and zinc aluminum phosphate, which represents second generation of phosphate based anticorrosion pigments, on the performance of a polyurethane coating was studied. While zinc phosphate modification was proved to be effective on the corrosion resistance, EIS data facilitated the determination of the optimum pigment volume concentration in which the coating offered the most efficient protection. The superiority of zinc aluminum polyphosphate was attributed to the release of more inhibiting species, leading to the formation of a protective layer at the coating/substrate interface. In addition to the assessment of the impact of pigment content on the resistance of polyurethane primer to cathodic disbonding, the dependency of adhesion strength on the pigment type was also studied using pull-off test.     

Cathodic disbonding of a thick polyurethane coating from steel in sodium chloride solution

The cathodic disbonding of a thick, pigmented polyurethane coating from steel in 3.5 wt.% NaCl solution was studied by using an electrochemical AC impedance technique. Double-cylinder electrolyte cells were designed to separate the measurements of cathodic disbonding process from the influence of the impedance of an artificial defect. It was found that for a thick, pigmented polyurethane coating, the more important transport pathway of the reactive species is along the coating/steel interface rather than through the coating. There existed a delay time for the cathodic disbonding process, and cathodic polarization was not a predominant factor in determining the cathodic disbonding behavior in the early stages. The thick polyurethane coating, which was applied on a well sand-blasted steel surface, had excellent resistance to cathodic disbonding.     

Reduction of cathodic delamination rates of anticorrosive coatings using free radical scavengers

Cathodic delamination is one of the major modes of failure for anticorrosive coatings subjected to a physical damage and immersed in seawater. The cause of cathodic delamination has been reported to be the result of a chemical attack at the coating–steel interface by free radicals and peroxides formed as intermediates in the cathodic reaction during the corrosion process. In this study, antioxidants (i.e., free radical scavengers and peroxide decomposers) have been incorporated into various generic types of coatings to investigate the effect of antioxidants on the rate of cathodic delamination of epoxy coatings on cold rolled steel. The addition of <5 wt% free radical scavengers to epoxy coatings improved the resistance toward cathodic delamination by up to 50% during seawater immersion, while peroxide decomposers had a limited effect. Testing using substrates prepared from stainless steel, copper, aluminum, galvanized steel, and brass also showed a reduction in the rate of cathodic delamination when the coating was modified with a free radical scavenger. The protective mechanism of free radical scavengers investigated for the primers are similar to that of antioxidants used for protection against photochemical degradation by UV-radiation of top coatings. Both substrate corrosion and degradation of a coating exposed to UV-radiation lead to the formation of free radicals as reactive intermediates.