Precision Environmental gaseous pollutants

Sulfur-containing gases, such as carbon dioxide (SO2) and hydrogen sulfide (H2S), is caused by corrosion of the most common electronic devices gas (R ice et al.1981). For example, compliance with Restriction of Hazardous Substances Directive RoHS) (EU 2003) gas pollution board corrosion, shown in Figure 1.
ANSI/ISA-71.04-198 environmental constraints have been released gas composition. These limits determine the data center forEnvironmental cleanliness has a guiding role, however, for some reason, for measuring or predicting thecorrosive environment in the data center hardware failure rate, they do not have any help. First, determine the gas composition is not a simple task. Secondly, in general, by the gas component to predict the corrosion rate is not a very intuitive work. Synergy between the gas makes the situation even more complicated. E.g., confirmed, sulfur orhydrogen sulfide, and silver or copper itself is not very strong corrosion, but when they are combined with other gases (such as nitrogen dioxide and / or ozone), silver and copper will produce a strong corrosive (Volpe 1989). Effect of relative humidity has a great rate of corrosion of copper, silver and the corrosion rate was independent of humidity(Rice 1981).

As described ANSI/ISA-71.04-1985 standard , to determine corrosive gases within the data center environment , there is a very simple way to quantify the so-called " reactive monitoring method ." This method will be placed in the context of copper samples a month , and then use the Coulomb reduction method to analyze the thickness and chemical properties of corrosion products , the environment and thus classified as described in Table 2 of the four severity levels in one . According to ISA-71.04, in the case of adequate control environment , the corrosion rate of copper should be less than 300Å / month, corrosion is not a factor in determining the reliability of the device. However, there are only two copper specimens major limitations : First, for many metals strongly corrosive chlorine contaminants , the copper is not very sensitive ; Second , the degree of corrosion of copper and too sensitive to relative humidity . Silver samples help distinguish the effects of relative humidity on the corrosion caused by gaseous pollutants. If the results show that the relative humidity has a significant effect on the corrosion process , simply reduce the relative humidity of the data center can be reduced by corrosion . The method is now common use of silver and copper specimen sample , in order to better understand the environment in the chemical properties of the etching gas .
2009 White Paper recommended ASHRAE particulate and gaseous contamination , copper and silver corrosion rate should be less than 300 Å / month