Purpose

The purpose of this paper is to study the susceptibility of these three commonly used corrosion resistance fasteners in seawater. For a more practical scenario, a local Atlantic coastal seawater as received was used.

Design/methodology/approach

Carbon fiber reinforced polymer (CFRP) was fabricated with T700 carbon fiber (Toray Inc.) and VE8084 vinyl ester resin (Ashland) to make a unidirectional composite panel of thickness 1.8 mm. A conductive paint was applied to one of the sample edges that was perpendicular to the fiber direction, providing an electrical contact with carbon fibers to connect a copper wire. This external electric connection was used for potential measurements of both the open circuit potential (OCP) of the CFRP sample, and the mixed potential of the fastened set: consisting of the CFRP and the metallic fastener fastened to it. Three common fastener alloys were selected: 316SS, Monel and Titanium. For this purpose, a high impedance voltmeter was used in conjunction with a saturated calomel reference electrode. Measurements were taken daily. For longer time measurements, a four-channel high impedance analog data logger was used with 30 min sampling rate.

Findings

For both 316SS and Monel fastened sets, crevice corrosion occurred inside the occluded regions of the set, when immersed in coastal seawater. The attack was more severe for 316 stainless steel set. An isolated island attack of faceted surfaces morphology was seen for 316SS set. While, a circular ring of preferential grain boundary attack appeared for Monel set, indicating an IR (voltage) drop mechanism is more likely operating. Titanium-fastened sets showed high resistance to crevice corrosion when simmered in seawater. However, for long-time exposure, the sets became more susceptible to crevice corrosion attack supported by CFRP attachment (oxygen reduction reaction taking place at the carbon fibers).

Originality/value

Evidently, titanium, stainless steels and Monel are good candidates for galvanic corrosion resistance. However, their susceptibility to crevice corrosion when coupled with CFRP is a new challenging topic that needs further investigation. This is very important today because the vast application witnessed for CFRP material. This work involves developing an original methodology for this kind of investigation and was done at advanced laboratories of SeaTech at Florida Atlantic University by the Atlantic coastline.

中文翻译：

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暴露于沿海海水的碳纤维增强聚合物 (CFRP) 金属紧固接头缝隙腐蚀研究

目的

本文的目的是研究这三种常用的耐腐蚀紧固件在海水中的敏感性。对于更实际的情况，使用了当地大西洋沿岸的海水。

设计/方法/方法

碳纤维增强聚合物 (CFRP) 由 T700 碳纤维 (Toray Inc.) 和 VE8084 乙烯基酯树脂 (Ashland) 制成，制成厚度为 1.8 mm 的单向复合板。将导电涂料涂在垂直于纤维方向的样品边缘之一上，提供与碳纤维的电接触以连接铜线。这种外部电连接用于测量 CFRP 样品的开路电位 (OCP) 和固定装置的混合电位：由 CFRP 和固定在其上的金属紧固件组成。选用了三种常见的紧固件合金：316SS、蒙乃尔合金和钛合金。为此，将高阻抗电压表与饱和甘汞参比电极结合使用。每天进行测量。对于更长时间的测量，

发现

对于 316SS 和 Monel 紧固装置，当浸入沿海海水时，装置的闭塞区域内会发生缝隙腐蚀。316 不锈钢组的攻击更为严重。对于 316SS 组，观察到小平面形态的孤立岛攻击。同时，Monel 组出现了优先晶界攻击的圆环，表明 IR（电压）下降机制更可能起作用。钛固定装置在海水中炖煮时表现出很高的抗缝隙腐蚀能力。然而，对于长时间暴露，这些装置变得更容易受到由 CFRP 附件支持的缝隙腐蚀攻击（碳纤维上发生氧还原反应）。

原创性/价值

显然，钛、不锈钢和蒙乃尔合金是耐电偶腐蚀的良好候选材料。然而，当与 CFRP 结合使用时，它们对缝隙腐蚀的敏感性是一个新的具有挑战性的课题，需要进一步研究。这在今天非常重要，因为 CFRP 材料有广泛的应用。这项工作涉及为这种调查开发一种原始方法，并在佛罗里达大西洋大学的 SeaTech 高级实验室完成，靠近大西洋海岸线。