Effects of NaCl Concentration and Solution Temperature on the Galvanic Corrosion Between CFRP and A516Gr.55 Carbon Steel

Abstract

About 20 ~ 50% of typical carbon fiber reinforced plastic is lighter than metals, and CFRP has excellent properties, including low density, high strength and high corrosion resistance [1,2]. Because of these excellent properties of CFRP, composite materials which meet various regulation conditions needed in the industrial fields, have been widely used in the many industries including aircraft, transportation, ship building, and automobile etc. [3,4]. However, CFRP reveals water absorption in water immersion or high humidity environment, and water absorption occurs in an epoxy not carbon fiber, and can be facilitated by higher temperature. Since these properties can induce volume expansion inside CFRP and change the internal stress state and degrade the chemical bond between the fiber and the matrix, the mechanical properties including bond strength may be lowered [5,6]. When CFRP contacts to metallic materials, galvanic corrosion can be occur because of the potential difference between them [7,8]. Galvanic corrosion is known to occur when two dissimilar materials are jointed together. In general, the less noble material experiences accelerated corrosion [9]. Corrosion of metallic materials varies with the exposure time in the environments, and it depends upon the formation of protective passive film and microstructure [10] and the ratio of cathode and anode, corrosivity, and temperature etc. [11]. Our group has recently reported the galvanic corrosion between GECM (Graphite Epoxy Composite Materials) and aluminum/carbon steel [12-14]: In galvanic couple between aluminum and carbon steel bolt, their corrosion rates were higher than those of single specimen. In galvanic couple between GECM, aluminum, and carbon steel, corrosion behavior of carbon steel bolt and aluminum was changed due to different corrosion mechanism in tap water and chloride solutions. On the other hand, it is well known that a strong galvanic couple can be formed between CFRP and steel rivets if the joint is exposed to a corrosion environment. In general, CFRP is cathodic and performs Effects of NaCl Concentration and Solution Temperature on the Galvanic Corrosion Between CFRP and A516Gr.55 Carbon Steel