51315-5692-Correlation of Laboratory and Field Exposure of Localized Corrosion at Magnesium-Ceramic Interfaces

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Product Number: 51315-5692-SG

ISBN: 5692 2015 CP

Author: Raghu Srinivasan

Publication Date: 2015

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Interests in providing greater ballistic protection at lower weight has made magnesium alloys such as AZ31B candidate materials for hybrid armor systems. Unique characteristics like superior vibration damping of magnesium in comparison to other armor metals (e.g. steel and aluminum) could result in better shock mitigation and overall ballistic performance. The hybrid ceramic-metal armor system consists of a ceramic plate or tile bonded to a metal backing plate. The ceramic tile faces the incoming projectile and shatters it on impact. In the process the ceramic tile is also subjected to localized fracture which absorbs the kinetic energy of the impact. The backing metal absorbs the residual energy and keeps the fragments of the ceramic tile together which also gives the ceramic-metal armor system multiple hit capabilities. This armor system consisting of dissimilar materials can lead to corrosion problems such as crevice and or galvanic corrosion at the interfaces. Hence the corrosion performance of these advanced systems and their constituent needs to be investigated to define their limits of chemical stability. Testing in diverse natural environments improves understanding of realistic performance in the field.The main objective of this research is to develop test protocols and to analyze the corrosion of the AZ31B-H24 magnesium alloy coupled to a silicon carbide (SiC) ceramic in natural-exposure and accelerated corrosion tests. The focus will be on correlating outdoor exposure corrosion behavior from a variety of microclimates with a series of accelerated laboratory corrosion tests. The use of hybrid ceramic-polymer or ceramer coatings was also investigated to attenuate corrosion at the SiC-magnesium interface.Initial six-month exposure results showed the interfacial Mg corrosion rates at the Mg-SiC interface were much less severe than the general corrosion rates outside of the crevice. The mass loss of uncoupled AZ31B Mg was higher than that of the coupled samples due to corrosion suppression in the interface regions. Future experiments include correlation between the corrosion rates and the weather parameters for the two exposure periods for the outdoor experiments. Anodic and cathodic polarization of AZ31B Mg help elucidate the attenuation of corrosion inside of the interface. Analysis of the ingress of environmental constituents across the interface using scanning electron microscope (SEM) and energy dispersive-X-ray analysis (EDXA) are also planned.