What Problems Might You Experience When Joining Different Metals Together?

Obviously, not all metals are constructed in the same way. They all have different structures and metallic combinations and come in different weights and properties that need to be considered. Some metals melt at a higher temperature than others, while others are so heavy that care needs to be taken when combining them. Today, we’re going to look at the problems you might experience when joining different metals together.

Galvanic corrosion

This is a fancy way of saying that one of the two metals you’re considering joining together is more likely to experience corrosion. Thanks to different molecular structures, one of the adjoining metals might start corroding in an electrolyte solution due to the way it has been combined with the other metal. This occurs primarily in ferrous metals such as iron, when they’re combined with another metal. A common solution is to put protective sheets of unreactive metals in between the join.

However, even these reactive metals might start to galvanise and cause corrosion, meaning they might require maintenance and, eventually, replacement.

Differences in melting temperatures

This can be a big problem - especially if you’re considering welding and fusing two dissimilar metals. For instance, tin has a melting point of 231.9 degrees Celsius, while steel has a melting point somewhere in the region of 1371-1510 degrees Celsius, depending on what type of steel it is (either carbon or stainless). This means that if you’re considering welding two pieces of dissimilar metal together, you might have to rethink your strategy or consider using extra metal. The latter solution enables you to use the additional, melted metal to ‘weld’ the other two pieces together.

Thermo expansion effect

Another factor to consider is the cooling and expansion effect. It’s important to note that the cooling and expansion of metal are not directly correlated. For example, the hotter metal needs to burn, the more significant the expansion. Aluminium is the most common metal that can be affected by expansion due to heat, due to the fact that its melting point is in the mid-range compared to other metals.

This needs to be factored in when there are size constraints during construction – particularly when you bear in mind how the expansion might affect the metal on the production line.

Adhesive bonding

Another method that’s used for joining metals together is adhesive bonding or industrial glue. These are very strong adhesives and should always be handled with care. While incredibly effective at joining metals together, a major problem that can result from the use of adhesive bonding is additional weight. No two types of metal weigh exactly the same, and, depending on how two pieces of metal have been joined, the extra leverage from one side can cause the join to fail.

Using rivets

If you need only a semi-permanent solution, you might consider joining metal together with riveting. Just keep in mind that you’re actually making both metals weaker with this method by placing holes in the metal itself, thus reducing its strength. Usually, with riveting comes extra support materials that can be locked into place to provide the extra strength and leverage needed when two dissimilar metals have opposing weights.

However, riveting might not work with all-metal types as the holes themselves might cause too much damage.

If this sort of thing interests you then don’t forget you can contact the Flowdrill team directly - we’d be delighted to hear from you.