From commercial airliners to performance military jets, a majority of aircraft are manufactured from aluminum. This is due to the high strength-to-weight ratio that aluminum provides, allowing reliable assemblies that excel in heavier-than-air flight. While aluminum is highly beneficial for the construction of aircraft, such materials limit the fastener types that may be used to secure parts together based on their material. When two or more dissimilar metals are pressed together with pressure, corrosion may occur and result in irreparable damages. Despite such issues, avoiding fastener and surface corrosion simply requires choosing fastener materials that can accommodate aluminum structures.
Coated steel is a popular material choice for aerospace construction, due to the fact that coatings can protect aluminum surfaces from corrosion. It is crucial that coatings are thick enough for certain materials, as missing coatings can cause an exposure to dissimilar metals and thus corrosion. Across most coated steel fastener types, the most popular are those that are mixed with zinc. As zinc is a noncorrosive element, flakes can be deposited into the binder of the fastener for surface protection. As there are no fasteners that utilize aluminum flakes, zinc coated steel serves as an optimal option. When implementing coated steel screws, bolts, or nuts, one may add a layer of paint in order to improve protection. Nevertheless, paint can easily come off over time and during installation, thus should not be relied on as the main form of material protection.
As one of the original methods of coating steel, galvanization may be used to protect aluminum surfaces from fasteners. As a form of electroplating, galvanization consists of producing a corrosion-resistant layer on either the surface of the aircraft or the fasteners installed on them. Due to the method of using electricity for galvanization, the bonds formed between metals and protective coatings are very rigorous and secure. Despite this, installation and normal operations can eventually wear away the coating and cause scratching. As such, many aircraft manufacturers have since moved on to more robust options that provide more durable coatings. As compared to standard coated fasteners, galvanized fastener types are capable of providing the same resistance to corrosion while often remaining lower in cost.
When two dissimilar metals are placed against each other and are affected by the presence of moisture, galvanic corrosion may occur. With such an exchange, one metal may become very weak and lose its structural integrity. To avoid this, the same metal may be used as possible. While aluminum fasteners would avoid galvanic corrosion, such materials are not sufficient in their shearing resistance. Despite this, aluminum fastener types may still be used for the construction of aircraft assemblies, albeit for areas that are less heavy-duty.
As the final common option for fastener materials, there are many screws, nuts, and bolts that may be produced from non-metal materials. With high-strength plastics, assemblies can be secured without the worry of metallic corrosion due to dissimilar metal materials. As compared to fasteners constructed from aluminum, non-metal
bolts and screws tend to feature even less strength. As such, they are most often implemented in low-stress assemblies and excel in medical and food-manufacturing areas.
Altogether, the galvanized steel fastener type serves as the most optimal choice for aircraft construction with its capabilities and characteristics. Despite this, other materials can still be useful to accommodate a variety of assemblies and applications. At
ASAP Sourcing Solutions, we can help you secure the
aircraft fasteners that you need with competitive pricing and rapid-lead times. To guarantee the quality of our offered parts, everything has been thoroughly tested for quality assurance and all items ship alongside their qualifying certifications or manufacturing trace documents. If you have any questions or concerns regarding our services or purchasing process, our team of industry experts are readily available 24/7x365 and may be reached by phone or email.