As a fastener business we often get some hard questions about fasteners. Sometimes though, we get questions that seem obvious to us because we have been in the industry for so long. Its hard to tell when something is common knowledge or simply something we know because we work in the industry. To remedy this, we highlight 1 quick tip each week for using fasteners that outline some of the basics of fasteners we think everyone should know. And, this week we focus on why you shouldn’t use stainless steel and aluminum together.
Tip number 1 for superior performing fasteners
Why you shouldn’t use 18-8 stainless steel in or near a salt water environment
Salt water is great at causing rust and reducing the life of fasteners. To remedy this, we recommend using stainless steel, but it is important to use the correct grade of stainless steel. We recommend using only a 316 grade stainless steel within 32 kilometres of the salt water environment. Otherwise the risk of oxidisation (rust), even in other grades of stainless steel, are greatly increased. Galling or cold welding can also occur when the same grade of stainless steel is used. When the same grade of stainless steel is used they can also stick or weld together. That’s why we recommend you use a 304 grade bolt with a 316 grade nut.
Tip number 2 for superior performing fasteners
Why you should always use hot dip galvanised fasteners with other hot dip galvanised fasteners
We coat Hot Dip Galvanised fasteners in a thick zinc protective, called hot dip galvanisation. Consequently, it makes them less susceptible to oxidisation. This thick coating creates a layer on the threading that will not match other materials that do not have this coating. Fasteners that get hot dip galvanised and have different spacing in preparation for this change in thickness. As such, they should only be used together to avoid any compatibility issues.
We further recommend that when installing fasteners you always try to use the same grade and material. Mixing can lead to uneven or poor results depending on the materials.
Tip number 3 for superior performing fasteners
Why you shouldn’t use stainless steel and aluminum together
Stainless Steel and Aluminum are metals that have very specific cases where they can be used together. Therefore, if you use them together improperly, there will be a transfer of electrons between them which can compromise the integrity of the materials leading to what is called galvanic corrosion. But the easiest way to avoid galvanic corrosion is simply to use materials that match.
Note that Stainless steel is considered to be a soft metal. There are versions that can become hard metals by heating them up to change stainless steel’s properties.
