How To Solder Aluminum With Soldering Iron

It’s a common belief that soldering aluminum is a complicated task. 

In fact, a few years ago, I thought so too. That’s why I always preferred getting it done by a professional. But soon, I realized that a lot of money was going into this and thought I should try it at least once, given that I had often soldered other metals for various purposes. 

Thus, I started researching simple procedures for soldering aluminum and soon found out that a soldering iron can be of great help in this regard. Delving deeper into the details helped me figure out the procedure properly, and in no time, I was all set to begin my first aluminum soldering project. 

Since then, I’ve come a long way and have managed to cut the extra spending by soldering all of my aluminum objects by myself!

Hi! This is Stacy, and today, I’ll be answering the question "How to solder aluminum with soldering iron?" Let’s begin then, shall we?

How To Solder Aluminum With Soldering Iron

When it’s about soldering aluminum objects using a soldering iron, you must consider several important factors beforehand. This will ensure that the soldered object is efficient enough for later use. As such, I’ll discuss each of these factors briefly before moving over to the procedure.

Things To Know Beforehand

The first thing to note is that aluminum is a metal having a melting point lower in comparison to many others, i.e., about 660°C. This implies you’ll have to use a unique product for soldering that also has a melting point much lower than other soldering tools. 

In addition, you must remember that aluminum oxide that’s often found on the surface of most aluminum objects cannot be soldered. This is why you should scrape it off entirely before starting the procedure. Note that for heavily oxidized objects, you can sand, grind, or wipe them using acetone, as these will make the removal procedure quicker. 

This procedure is indeed really effective, as I could quickly remove all the oxide on one occasion when I had to solder such an object. Apart from this, here are some more points you must keep in mind, based on the object you’re soldering. 

A. Identify The Alloy

Most aluminum products that you’ll come across are actually alloys of aluminum, and they often come with a number or letter marked on the surface. So, make sure you look up that number or letter online to know if there's any specific requirement to adhere to for soldering that alloy.

B. Choose The Right Soldering Iron

While you’re purchasing the soldering iron, make sure to confirm that it’s specifically built for soldering aluminum-aluminum joints.

C. Use An Aluminum Solder Flux

Using a flux especially designed for aluminum is vital to the procedure. Hence, I purchased both the soldering iron and the flux from the same place, and I’d suggest you do this too.

The Procedure

With all the preparatory steps done right, you can start soldering the aluminum object soon after. Here’s how to go about it:

Step 1: Cleaning The Aluminum Object

To ensure that the soldering is perfect, cleaning the surface of the aluminum object is a must as it can give rise to an aluminum oxide coating on reacting with air. You can opt for a stainless steel brush for this purpose. 

In addition, you should clean the flux and soldering iron too so that all the possibilities of the oxide formation are ruled out. 

Step 2: Clamping The Metals Together

Firstly, keep in mind that you’ll only need to follow this step if you’re fixing two aluminum pieces. I only had to use this step once for fixing a break in an aluminum bracelet that was among my most cherished possessions. 

Clamp the two aluminum pieces together in the desired position. Also, there has to be a little gap between the pieces so that the soldering iron can flow easily. If you find that the pieces are not fitting together smoothly enough, enhance the smoothness of the joined place by sanding it. 

Step 3: Spread The Solder Flux

After you’ve cleaned the object, put the flux very carefully on the places that have to be joined. You must use a rod in the soldering iron or a tiny metal tool. This will help draw the soldering iron along the longest edge of the joint, besides eliminating further chances of oxide formation. 

Here, let me also tell you that in the case of soldering wires, you will require dipping them in liquid flux. But if the flux is in powdered form, read its label carefully to know about the mixing procedure. 

Step 4: Apply Uniform Heat

Now, heat the object or workpiece on the parts beside the joint using the iron for soldering. Note that you start with the lowest portion of the workpiece. 

Also, the direct flame applied to any one area for too long can result in overheating of the flux as well as the solder. That’s why you must ensure that the heat source is moved constantly in slow motion. Ultimately, this will help heat the area uniformly. 

I had once mistakenly held the flame over a single area, which resulted in uneven soldering on that part, so taking this precaution is crucial to the procedure. 

Step 5: Apply The Solder

Finally, drag the rod of the soldering iron while heating the area constantly, that is, heating from the other side of the aluminum object. Apply the soldering iron slowly to get an even result. 

In case you observe that the solder isn’t bonding to the object, check if there is a layer of aluminum oxide on the surface. Clean it immediately and repeat all the steps until you get the desired results. 

Final Words