Don’t miss out on 20% OFF all radiators! sale ends today!
Inside any radiator, whether it is aluminum or copper brass, lies a sneaky enemy that can take down your engine quickly if left unchecked—corrosion. You may be thinking “but aluminum doesn’t rust?” and you would be correct, aluminum doesn’t rust as rust is limited to steel and iron. Aluminum does corrode, however, through several different mechanisms, as does copper brass in specific scenarios. Seeing as how your radiator is made of one of these two materials and filled with water, all the components are there to help the natural corrosion processes take hold. Let’s see what we can do to stop it.
Cathodes, Anodes, And You
The biggest threat to your cooling system is galvanic corrosion (not to be confused for electrolysis). This occurs when two dissimilar metals are connected through an electrolyte (such as water) along with a nearby source of EMF radiation (Electromagnetic Frequency). EMF is everywhere, but in your vehicle, there are multiple sources, from the alternator and battery, any one of a thousand electric motors, even the bearings in the water pump generate EMF when spinning. This process needs a positive metal (cathode) and a negative metal (anode), which one simply depends on the placement of the metal on the nobility scale. The higher the nobility, the less likely that metal gives up its ions in this process (more on this later). The cathode leaches ions from the anode through the electrolyte solution (coolant).
All of this means that your entire cooling system is one giant galvanic battery. You can actually see this by probing the battery with a voltmeter. Place the positive probe to the battery positive, and the negative probe to the battery negative, you should see around 12 volts. Move the negative probe to the radiator, and you will likely see a higher voltage, typically around .5 to 1 volt. The problem with this is that galvanic batteries literally eat themselves until the anode is gone. While this takes a long time, thin radiator tubes can develop pinholes quickly enough, which leads to overheating.
Copper Brass
While Copper Brass is inherently resistant to corrosion in the presence of water, it is not resistant to galvanic corrosion. Copper brass is incredibly effective at exchanging heat, making this material ideal for use as a radiator, but the construction of these radiators makes them more susceptible to galvanic corrosion. It is specifically the solder portion of the radiator that is the issue. Copper is very high on the nobility scale but lead and tin are quite low. In this scenario, the copper brass is the cathode, solder the anode, and over time, the ions from the solder leach into the cathode, weakening the joint and you spring a leak.
Aluminum
OK, I’ll just run an aluminum radiator then, all better.” Not so fast there, Sugar Plum, we aren’t finished yet. Aluminum is even more susceptible to this process because aluminum is lower than lead and tin (solder) on the nobility scale, in fact it is the second lowest, so instead of the solder being eaten, the entire radiator is one giant anode just freely giving up its delicious ions to every other metal in cooling system including iron and steel, so you may have jumped out of the frying pan and into the fire.
Aluminum has a natural oxide layer that forms immediately after being removed (this is why you have to scrub aluminum before welding it), so there is slightly more resistance, but when an aluminum radiator is used with an engine that is not entirely aluminum (block and heads), the risk factor goes up. An iron block will absolutely leach ions away from the radiator without hindrance.
Electrolysis
Galvanic corrosion is often referred to as “electrolysis”, but this is not quite accurate, as they are related but not the same. Electrolysis is the same process but boosted by adding electrical current instead of EMF radiation. This occurs in a cooling system when the engine does not have an adequate ground. Electrical current always seeks the path of least resistance, as wires age the resistance goes up, making it harder for current to flow through it. Loose fasteners, moisture, high heat, and other factors worsen the resistance, and it is not uncommon for electrical current to flow through the coolant seeking a path to ground. Coolant is an electrolyte; it passes electricity quite well.
Unlike slow moving galvanic corrosion, electrolysis is supercharged corrosion, it does not take long to destroy parts. In fact, it can kill a radiator in days if the current is strong enough. Anything over .03 volts through the coolant is too much.
Ground Game
Enough doom and gloom, let’s solve this problem. First, grounds are critical for every electrical system, make sure they are good. Replace or upgrade your battery negative leads to the engine block and heads (yes, both, especially if you have an iron block and aluminum heads), chassis/frame, and the body. Add a ground strap to the radiator. This can be attached via a mounting bolt, petcock drain, or pipe fitting. If the radiator is grounded, the circuit for electrolysis is neutralized.
Second, never use tap water in the cooling system. Tap water is full of minerals that enhance both galvanic corrosion and electrolysis. Only used pure distilled water mixed 50/50 with the correct antifreeze (see our article on antifreeze here). The best bet is to use a pre-mixed coolant, you are not “wasting money on water”, you are paying for the RIGHT water that will protect your vehicle.
The final solution is adding a sacrificial anode to the cooling system. The lowest metal on the nobility scale is zinc, which is why it is used for this purpose. A small zinc anode that threads into a port on the radiator does not stop galvanic action, but instead provides the yummy ions noble metals crave, instead of the aluminum or solder in the radiator. These are often threaded into the drain port, but if you do not have a good port available, zinc anodes are also available as a drop-in bar.
Your vehicle’s radiator is an investment in your drivetrain. You may have $10-20k in your engine, but a tiny pinhole in your radiator can destroy it in minutes. Don’t take chances, upgrade the grounds, add a sacrificial anode, and use the right coolant to ensure that your vehicle keeps on keepin’ on. Call U.S. Radiator today at 800-421-5975 to discuss the options for your vehicle.