2.2.3.3 External Environment and Humidity

2.2.3.3 External Environment and Humidity

When designing parts and components for external use, it is important to consider environmental factors other than temperature. Humidity and moisture can have a detrimental effect on many materials and joining methods. Vehicles produced in the automotive industry several decades ago were plagued by rust and corrosion issues in seams and body panels, as well as rivets and other mechanical joining methods. Beyond basic consideration of the substrate materials and the most suitable method of joining, protective coatings, paints and finishes can be applied to increase the durability and longevity of the components. Overall, the critical performance factors driving the development and use of coating technologies to protect exposed surfaces are (a) aesthetic characteristics, (b) corrosion protection, (c) mass production, (d) cost and environmental requirements and (e) appearance and durability.³ Although the relative importance of each of these factors is debatable, the perfection of any one at the expense of another could be unacceptable and uncover hidden flaws in the design or material selection. These are key points to note, particularly when selecting metals that are not known for long-term resistance to moisture and humidity, such as iron or steel, or when such materials are not pre-treated to achieve the necessary long-term performance, i.e. raw aluminium is known to corrode, while anodised finishes will offer longer lifespans without showing signs of degradation.