# Durability Issues and Corrosion of Structural Materials and Systems in Farm Environment
## 2 Agricultural Concrete and Metallic Structures
### Specific Impact of Corrosive Agents on Steel Reinforced Concrete Structures  
Metals are highly susceptible to corrosion following exposure to acids, alkalis, chloride, and ammonium containing solutions. The severity of the corrosive effect is influenced by the presence of H+ and OH- and the composition of the metallic structure. The incorporation of Cr-Ni into traditional steel increases the level of resistant to organic acid attacks [2]. Therefore, agricultural concrete structures reinforced by stainless steel, chromium steel, and chromium-nickel steels have a lower risk of structural failure compared to plain steel, aluminum, or zinc. On the downside, higher durability is offset by the costs associated with the treatment of the metallic structures. The impact of acetic acid on iron, steel, and zinc structures is considered in the next section. The impact of acetic acid on steel and iron is dependent on concentration and temperature. On average, the material corrodes by about 0-79, 1-2.3, 1.34 mm/year in a concentration of 15-33% acetic acid, respectively [2,7]. The corrosion of chromium steel by acetic acid follows a similar approach as the corrosion of steel and iron. However, the risk of corrosion is considerably lower in chromium steel, given that the materials corrode by less than 0.11 mm/y in 10% acetic acid [2,7]. Austenitic chromium and nickel steel materials are resistant to acetic acid corrosion. The corrosion of chromium steel by acetic acid follows a similar approach as the corrosion of steel and iron. However, the risk of corrosion is considerably lower in Chromium steel, given that the materials corrode by less than 0.11 mm/y in 10% acetic acid [2,7]. Zinc structures are severely corroded, even in low concentrations of acetic acids 0.01 and 0.1% acetic acid [2,7]. However, the acid attack only occurs in the presence of oxidizing agents. Therefore, the elimination of oxidizing agents should diminish the risk of corrosion. Similar to other metals, the risk of corrosion is most pronounced at higher acid concentrations. Iron and steel show some form of resistance to chloride solutions consisting of alkaline earth metals. The observation only applies if chlorides are present as solutions with alkali earth metals. However, the level of protection against corrosion is not absolute. Chromium steel is entirely resistant to corrosion induced by alkaline earth metals-chloride solutions. Chromium and nickel steel exhibit resistance against chlorides and chlorinated water. Zinc metal and structures exhibit weakened resistance to attack by acidic chlorides and chlorinated water. However, the risk of corrosion is substantially diminished in basic chloride solutions due to the formation of a protective layer. Aluminum structures  
Figure 1: SEM images illustrating the impact of corrosive acids on concrete exposed to chicken coop [6]. **(a)** shows the virgin external plate before acid attack while the micrographs labeled **(b–h)** show the progression of the acid attack and the changes on the surface and cross-sectional morphology. have no resistance to chloride-containing solutions. However, the risk of attack is mitigated by the incorporation of inhibitors such as tolytriazole or sodium silicate [2; 7]. Pitting corrosion has been observed following the exposure of aluminum to 10% calcium chloride solutions. Steel structures are also corroded when exposed to gases containing ammonia, such as ammonia hydroxide. Therefore, the risk of corrosion could be partially mitigated by regulating the temperatures. Chromium-nickel steel structures are resistant to corrosion induced by ammonia containing solutions. Zinc structures are resistant to ammonia gas. However, they are susceptible to corrosion induced by ammonium hydroxide. The latter solution has been proven to lead to a rate of corrosion of about 0.14-0.37 mm/year in 3-55% ammonium hydroxide solutions, even at a neutral pH [2; 7].