Unfortunately, these are also very critical joints in the structural integrity of the truss. Moderate corrosion has occurred at the heel connection of the trusses in this naturally ventilated swine barn. There are many potential causes of corrosion in animal buildings. Animals exhale large quantities of moisture into the air. This creates high relative humidity in the building if the moisture is not properly vented.
High humidity increases the potential for condensation which wets the entire truss assembly.
Ammonia gas, typically found in animal environments combines readily with this moisture and becomes ammonium hydroxide. This chemical attacks most metal surfaces. Free moisture on poorly protected steel will also initiate the rusting process. The moist wood accelerates the corrosion of the metal fasteners since wood itself is slightly acidic. Dust, commonly found in animal environments, provides a surface on which acids and gases can react, significantly accelerating the rate of corrosion.