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→13.5.4 Corrosion Testing
Battelle (the Battelle Institute) has, for different applications, defined four climate classes which reflect the corrosion behavior of porous electroplated gold surfaces. Such gold layers are often used in connectors for the telecommunications and information technology (<xr id="tab:Classification of Corrosion Effects According to Battelle"/><!--(Tab. 13.5)--> and <xr id="fig:Influence of the corrosive gas concentration for four classes"/><!--(Fig. 13.14)-->).
<figure id="fig:Influence of the corrosive gas concentration for four classes">
[[File:Influence of the corrosive gas concentration for four classes.jpg|right|thumb|Figure 1: Influence of the corrosive gas concentration for four classes (I–IV) on the contact resistance of a porous gold layer as a function of the exposure time (Battelle)]]
</figure>
<figtable id="tab:Classification of Corrosion Effects According to Battelle">
The dominant corrosion effects for thin gold coatings are pore corrosion and at higher gas concentrations creep corrosion from the base materials onto the coating, starting at the boundary line between non-precious base metal and contact layer.
The measurement of contact resistance allows an indirect classification of corrosion product layers. While the analysis of thicker corrosive product layers in the range of 0.1 – 1 μm can be performed by classic methods such as SEM and X-ray microprobe, thinner layers of 10 – 100 nm require the use of ionoptical analysis equipment.
