High heat dramatically increases the rate of oxidation on your soldering iron’s tip,
Is this the only reason why would your soldering iron tip turn black?
In This article, we will see why does it turns black & how it effects your soldering irons performance.
Not only that, but we will also see how you can Prevent your Soldering iron Tip from turning black.
Why does my soldering iron tip turn black?
There are two kinds of black coatings that form on soldering iron tips and make them black. One is a very thin, oily discoloration that results from flux breaking down – this is completely harmless and you should not attempt to remove it. The other is a thicker, hard, rough material that is essentially normal rust, happening very quickly because of the high temperatures at which these tools are used.
If your soldering iron tip looks like the picture on the left below, what you’re seeing is the buildup of flux residue. The dark coating is oily and translucent, and has virtually no thickness to it. Trying to remove this will almost certainly damage your tool, and it doesn’t affect performance at all. However, if your tip looks like the picture on the right, you’re seeing the result of oxidation.
Any soldering iron tip will rust to some degree, and over prolonged use, significant degradation of tool performance is all but unavoidable. Just about any soldering iron will have replaceable tips for this reason. However, proper tinning of your soldering iron tip before use, proper application of flux, and simple cleaning with an abrasive tool like sandpaper or brass wool can drastically increase your tool’s lifespan.
For many years, soldering iron tips were usually made of pure copper. Copper is an excellent material for conducting heat, but it’s soft enough that it would often start to melt into the solder itself or into the workpiece being soldered. In the 1980s, it became standard to coat the copper tip in a thin layer of iron, which remains hard at higher temperatures and won’t easily break down or contaminate your solder or project.
The use of this iron coating introduced a new problem, however: iron oxidizes very quickly at high temperatures. Oxidation is the natural process by which metals break down in interaction with oxygen and moisture. In the presence of normal air, at normal temperatures, iron slowly turns into iron oxide, a dark, brittle substance. The transformation happens gradually, in layers, from the outside in – this is why old iron tools and structures turn brown and disintegrate over time.
High heat dramatically increases the rate of oxidation, effectively subjecting your soldering iron tip to months’ worth of rust within minutes.
How badly does oxidation affect soldering iron performance?
Iron oxide is a poor conductor of heat. If your soldering iron tip is covered with a thin layer of rust, you may find that you need to increase the temperature on your iron in order to successfully melt solder. You’ll also find that solder doesn’t flow nicely into a layer on the tip the way it should, instead forming a ball hanging loosely from the tip. This makes it much more difficult to apply solder properly.
If the damage is allowed to continue getting worse, the full thickness of the iron coating may rust through, exposing the copper core of the tip. This copper can begin to melt. This can contaminate your solder as copper leeches out, and can also cause uneven heating on the tip as parts of it become hollowed out.
How can you prevent soldering iron tips from turning black?
You can’t entirely prevent this process from happening, since soldering iron tips are made of materials that simply are not chemically stable in normal air, even at room temperature. However, proper use of your soldering iron, along with regular care and maintenance, can prevent, or at least delay, the thin layer of iron oxide that naturally forms on iron tips becoming a problem. There are three main aspects to this: tinning, using flux, and cleaning.
“Tinning” is the process of applying a thin layer of solder to the soldering iron itself. Once your iron is heated up for a job, wipe it on a wet sponge to remove old solder, and apply solder to the tip. If the tip is hot enough (normally at least 300°C) and relatively free of rust, the solder will flow up the tip and coat it. This prevents the tip from being exposed to oxygen and moisture – both necessary parts of the oxidation process – while it’s heated.
Flux is a chemical compound that assists in the soldering process. Its primary purpose is to strengthen the mechanical bonds formed by solder, but more importantly for our purposes at the moment, most types of flux also contain chemicals that react with iron oxide to effectively dissolve it. Typical solder wire includes a small amount of flux in its core, but you can also buy flux on its own. It is a translucent paste that comes in small metal tins. Dip a hot iron directly into the tin, and you’ll see some of the oxidation disappear in a puff of smoke.
It’s also a good idea to clean your iron tip regularly – at the very least, before you put it away, each time you finish a job. Light abrasive cleaning is best, using a substance that is harder than iron oxide but not hard enough to scratch off the intact iron coating itself. You can use sandpaper for this in a pinch, but a better option is a small container filled with brass wool. This allows you to stick the iron into the brass and twist it around to scuff the rust off while it’s still hot, without getting your fingers too close to the hot tip.
How do you restore and clean a black soldering iron tip?
If your soldering iron tip has built up more oxidation than you can address with typical maintenance, there may still be ways to clean it.
First, check for any signs that any part of the iron coating has entirely worn away. If there are holes in the coating through which you can see the inner copper core, and especially if the copper core itself has started to break down, there’s no fixing it; you’ll need to replace the tip.
If you’ve caught it before any catastrophic damage has happened, however, what you’ll need to do is use both chemical and physical cleaning to wear away the iron oxide coating in layers.
The physical cleaning is best done with a container of brass wool. As for the chemical cleaning, ordinary flux isn’t going to cut it at this level of decay. Instead, you’ll want to buy a compound specifically designed for cleaning rusted iron tips. This might be labeled “tip tinner” or “tip activator”. Confusingly, you may find that both chemical compounds and containers of brass wool are also labeled as “tip cleaner”. Remember that you will need both.
Heat your soldering iron up to the low end of a typical work range, generally between 280 and 320°C. push the soldering iron tip into the chemical cleaner until the entire rusted area is submerged. Leave it there until the paste melts around the tip. Then push the tip into the brass wool and twist it back and forth. You should see the thickness of the oxidized layer reduced, as the cleaning paste will have weakened the iron oxide enough for the brass wool to scratch it off the tip.
You will likely need to repeat this process several times. Keep going until all the oxidation is removed. When you’re done, there will likely still be a layer of flux residue present making the tip look darker than when it was brand new. If you’re not sure whether what you’re looking at is flux residue or you still have rust to remove, try tinning the tip with solder. If it flows properly and covers the tip, your tool is “functionally clean”. If it balls up and hangs off the tip, you still have more rust to deal with.
Do soldering tips wear out?
Unless you’re doing all your soldering work in the vacuum of space or an oxygen-free cleanroom, an iron tip is going to rust over time, and there’s nothing you can do to prevent that entirely. All but the cheapest soldering irons are designed with replaceable tips. Replacement tips are inexpensive, with even the highest quality ones coming in at just a few dollars.
My soldering iron isn’t tinning – what are the causes?
If your soldering iron isn’t tinning, it’s very likely the first sign of problematic oxidation. Try the cleaning procedures outlined above with Brass wool & Tip Tinner. You might also be working at the wrong temperature for the solder, so check the solder packaging and adjust your iron temperature accordingly.
How long should a soldering iron tip last?
The lifespan of a soldering iron tip is actually quite variable, and comes down to both your care and maintenance and the tool’s construction. Not every tip is the same, and the thickness and purity of the iron coating may vary from one tool to another. Cheap tips that are included with inexpensive soldering irons, or sold in packs of a dozen replacement tips for $10 on Amazon, may wear out in a matter of weeks with even proper use and conscientious cleaning. A higher-quality tip, with proper care and maintenance, may last you for years.
How do you know if a soldering tip is bad?
A soldering iron tip is beyond any hope of effective cleaning or repair if any part of the iron tip, no matter how small, has worn all the way through. If you clean off the rust and spot a hole in the iron coating – recognizable by the copper color showing through from the inside – or if any part of the tip appears hollowed out, it’s done.
My soldering iron tip is burned out – what do I do?
It’s generally pretty easy to remove and replace the tip on most soldering irons. You can purchase a new tip online or at your local hardware store. This should go without saying, but if you’ve just been using (or trying to use) your soldering iron, let it cool down before replacing the tip! Once it’s cooled, look for a collar near where the metal part of the tool meets the plastic handle – unscrew this, and the end of the iron will come free. The replaceable tip is housed inside a metal sleeve. Discard the old tip, put the new one in its place, put the sleeve back on the iron, and screw down the collar.
Also Read: Soldering VS Welding