Corrosion Behaviour of Metal/Ceramic Interfaces in Physiological Solutions

Abstract

In this work the in vitro degradation behaviour of the metal/ceramic interface formed between c.p. titanium and a fluorosilicate machinable glass-ceramic joined by brazing alloys of the Ag-Cu-Ti system is studied in a simulated physiological solution. In the past, the degradation behaviour of the metal/ceramic interface (altogether, the metallic and the ceramic component plus the metal/ceramic interface), was investigated by means of standard electrochemical techniques [1][2][3]. In this work, standard samples, which are representative, in terms of chemical composition, of the most important layers present at the metal/ceramic interface, were prepared in an arc-melting furnace, which allows melting to be performed under a protective atmosphere (Ar). Electrochemical techniques and standard immersion tests were used to investigate the degradation behaviour of each individual layer existing at the metal/ceramic interface. The self-passivating behaviour of the interface, which was observed both in vitro and in vivo in previous works, can be better understood on the basis of the present results. The degradation behaviour of the individual layers is correlated with the overall corrosion behaviour of the metal/ceramic interface. Results suggest that Ag and Cu have an important role regarding corrosion behaviour: while Ag contributes to the passivation of the interface, the Cu-rich layer of the metal/ceramic interface seems to be responsible for the major part of the Cu ions released to the physiological solution.

Joining of engineering ceramics

“…Biomedical applications in which joining of ceramics is an issue fall into two broad categories: dental applications, in which for example titanium used as a dental prosthesis needs to be bonded to a dental porcelain or glass-ceramic, [345][346][347][348][349] and more general biomedical applications such as biomedical sensors, coatings on hip prostheses and microsystems for implantable applications in which there is a need for joining metals to ceramics. 348,350,351 Since ceramic biomaterials are not exposed to high temperature environments, low temperature bonding technologies such as the use of composite resin cements, zinc phosphate cements and glass ionomer cements can be used for bonding to dental ceramics and are widely used. 352,353 One application in which a purely mechanical fit is used is the attachment of ceramic femoral heads to femoral stems in prosthetic hip replacements.…”

“…347 Although a number of interlayers show promise, such as the use of gold as an interlayer, it is apparent that no interlayer has been yet found to be clearly superior to the others. An alternative technology reported by Rocha et al is to use Ag-Cu-Ti active metal brazing for titanium-ceramic joining, 348 the problem with this bonding technology is that an unacceptable level of copper ions are released into simulated physiological solutions when in vitro. Although hermetic protection of implantable microsystems is often achieved with metals such as titanium, tantalum or niobium, it can also be achieved with technologies such as anodic bonding of glass to silicon, which can produce hermetically sealed packages with a mean time to failure at body temperature greater than the lifetime of the patient.…”

Evaluation of Corrosion Resistance of Multi-Layered Ti/Glass-Ceramic Interfaces by Electrochemical Impedance Spectroscopy

“…Finally, at the glass-ceramic side (layers E 1 and E 2 ) accumulation of Ti and the presence of Si, was detected. In fact, the bonding with the glass-ceramic occurs because Ti is expected to reduce SiO 2 giving origin to both, Ti oxides and Ti silicides, these being the main constituents of layers E 1 and E 2 [2].…”

“…One of the most important joining techniques used to produce these joints is the active metal brazing procedure, which involves a brazing alloy, characterized by its low melting point, which is expected to promote a better wettability between both materials, metal and ceramic. From the corrosion point of view, one of the drawbacks of this methodology is the formation of a complex interface which, most of the times, is the critical region of the component [1,2]. It is recognized that when a multi-layered metal/ceramic interface is obtained, the degradation of the interface may be dictated by complex microscopic galvanic interactions between layers.…”

Brazing of ZTA ceramic with titanium for biomedical application

“…One of the main disadvantages of the Ag-Cu-Ti system, however, is the reason for the use of these alloys in medicine. In [22], the corrosion behavior of ceramic/titanium brazed compounds was studied using gravimetric tests. The results show that there is a relatively high yield of silver in the liquid solution, which is harmful to health.…”