# Durability Issues and Corrosion of Structural Materials and Systems in Farm Environment
## 3 Corrosion and Degradation of Structural Materials in Farm Environment
### Acid Corrosion Mechanism in Cement Structures
#### 3.4.3 Crop Storage Silos  
Apart from structures that are in direct contact with manure, agricultural effluents, waste, and other liquids, the durability of the materials used in the construction of silos is impacted by heat and moisture [11]. [PERSON] noted that silos constructed using galvanized steel were corroded over time, even though stainless steel offers long-term protection against corrosion. The corrosion was induced by the staining of the metal reinforcements by pulses, rapeseed, and wheat; it is of note that the process of corrosion progressed even though the produce was dehydrated to the required standards [11]. Beyond moisture, there were other factors that contributed to corrosion, including the fatty acids. Higher fatty acid concentrations translate to higher erucic acid. The rate of corrosion was most pronounced in mild steel compared to galvanic steel, as shown in Table 7[11]. The observation is consistent with [PERSON] and [PERSON] concerning the superiority of galvanized steel and chromium steel.  
The produce stored in silos is susceptible to insect infestation and has to be treated by insecticides, which can increase the risk of corrosion. Alternatively, the constituent components in rapeseed, such as glucosinolates, triggered enzymatic activity leading to cellular disruption, loss of physical integrity leading to the release of nitriles, formation of acids and ammonia, and corrosion in general. Even though the type of products contributed to the risk of corrosion, optimal mass losses were reported in cases where there was optimal relative humidity, as shown in Table 8.  
Supplementary explanation for Tables 7 and 8: The information in Table 7 show that the corrosion rate was higher in silos with 90% relative humidity and no oilseed rape. The least corrosion was  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & \multicolumn{3}{c}{**Corrosion Rate, mm Per Year**} \\
**\% Relative Humidity** & **No Oilseed Rape** & **with Oilseed Rape** \\ \hline
51 & \(0.6\times 10^{-3}\) & \(0.3\times 10^{-3}\) \\
75 & \(6.5\times 10^{-3}\) & \(2.6\times 10^{-3}\) \\
81 & \(4.9\times 10^{-3}\) & \(4.0\times 10^{-3}\) \\
90 & \(8.8\times 10^{-3}\) & \(2.0\times 10^{-3}\) \\ Saturation & \(8.6\times 10^{-3}\) & \(14\times 10^{-3}\) \\ \hline \hline \end{tabular}
\end{table}
Table 7: Relationship between relative humidity, rapeseed oil, and corrosion of silos [11]. “Reproduced with permission from Cleland, J.H., Eng. Fail. Anal. by Elsevier, 1994.”  
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Corrosion Rate, mm Per Year**} \\
**ime, h.** & 216 & 717 & 1173 & 1362 & 1674 & 2034 & 2319 \\ \hline Mild steel & 0.40 & 0.13 & 0.08 & 0.08 & 0.40 & 0.30 & 0.10 \\ Galv. steel \#1 & 0.35 & 0.09 & 0.08 & 0.07 & 0.06 & 0.06 & 0.05 \\ Galv. steel \# 2 & 0.30 & 0.10 & 0.06 & 0.06 & 0.04 & 0.02 & 0.02 \\ C.P. Zinc & 0.30 & 0.07 & 0.05 & 0.04 & 0.05 & 0.04 & 0.04 \\ \hline \hline \end{tabular}
\end{table}
Table 8: Rate of corrosion of metallic sections in silos [11] “Reproduced with permission from [PERSON], Eng. Fail. Anal. by Elsevier, 1994”.  
reported at 51% relative humidity. The data in Table 8 show that mild steel is more susceptible to corrosion compared to galvanized steel. Galvanized steel #1 had as-cut edges while galvanized steel #2 had \"had two coats of zinc-rich paint which overlapped the edges by 3.2 mm.\"