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The Best Rust Treatment For Cars

More than half of a car's entire structure is made from steel. While it has many benefits including actually supporting the weight of the car and aiding in crash protection, steel does have one mortal enemy - rust. Corrosion is one of the worst things that could ever manifest on any automobile. If not cured quickly, it can fester and eat its way through your car's steel bodywork and frame. 

While it doesn't happen so much on modern cars, it's still possible if left exposed in just the right conditions. The effects of this aren't just unpleasant to the eyes, but the rust could compromise the rigidity of your car. In short, rust is hideous and dangerously bad. If this is happening to you right now, what are the rust treatments and preventions that you should consider for your car?

Understanding Rust

Before we get into treatment, we should first pinpoint the exact cause of the rust itself. Otherwise known as oxidation, practically any form of metal is vulnerable. Despite the highly advanced alloys and coatings designed to deter it, the iron that forms a core part of metal could still rust in certain environments. Leave it for long enough, and metal will degrade and reduce into iron oxide.

This happens as the iron molecules at the surface react with oxygen. This reaction creates a new material to form, iron oxide, or more popularly known as rust. This is made worse with those clever alloys that we talked about. For all their added advantages such as greater tensile strength and its flexibility, alloys can add impurities that'll cause iron in the metal alloys to rust quicker.

Other factors could also accelerate this rusting process, such as a car's exposure to salt. Salts and contaminants on the road can mix with water, and turn into electrolytes. When exposed to iron within the metal alloys, this speeds up oxidation. There are, nonetheless, different types of rust. Each one will naturally have unique ways of treating and fixing it.

Treatment #1: Surface Rust

The first - and least serious - type of rust that you'll encounter is 'surface rust'. The name tells it all, as surface rust exists only on the surface of a metal structure or panel. Surface rust is mostly formed when there is mechanical damage - such as physical scratches - or through prolonged UV (sunlight) exposure. Hence, why even cars in warm and dry weathers are subject to surface rust.

Thankfully, surface rust isn't - at first, anyway - a serious issue. It hasn't penetrated deep enough into the rest of the metal alloy to cause any structural damage. On the contrary, depending on what the alloy is made from and how thick it is, that surface rust could actually start protecting the rest of the metal from further corrosion. Nevertheless, surface rust should still be looked into right away.

If you wait too long to fix it, a change in weather, for example, could start eating away the metal, and that surface rust will turn a lot more serious. Fixing surface rust is the simplest of the bunch and is quite similar to a lot of paint repair...

  1. Use an abrasive material like sandpaper to wear down the paint, and the corrosion respectively until the bright and shiny metal underneath is visible. It helps to sand a bit off the areas that surround the surface rust.
  2. Now, use special rust converters and removers to remove any further iron oxide on the alloy. These convert the iron oxide into other chemically stable compounds that can prevent rust from infecting the bodywork underneath. 
  3. Carefully apply the rust converters or removers using a brush or sponge (while wearing some rubber gloves), and wait 15 to 30 minutes for it to dry.
  4. Add a second layer of rust converter/remover, and wait another 30+ minutes for that to dry out.
  5. Keep the newly treated surface free from any moisture and contaminants for at least one day (24 hours), and then you can start by repainting the surface. Begin with a primer, followed by the base coat and clear coat.

Treatment #2: Scale Rust

Moving up a bit in terms of seriousness, we have 'scale rust'. While it may start appearing along the surface, you can start seeing bubbles forming in your car's paint. The outer layers of paint will then continue to expand until it cracks and flakes away, before unveiling the rusty hell below. This is where scale rust comes along, which can penetrate deep below the surface.

This very rough scale rust could sooner or later affect the strength of the metal alloy, and begin to compromise its rigidity. Scale rust is what happens when you don't treat surface rust right away. The fix for scale rust, consequently, needs to go a lot deeper than surface rust...

  1. First, you'll need to remove the scale rust, which may require using a wire brush, grinding wheel, and finishing off with some sandpaper. In this order, keep at it until the shiny bare metal appears, and there are no more flakes of rust anywhere.
  2. Again, sand and wear down a bit of material around the rusty areas. Now, you can begin to smoothen out the bodywork with some body filler. You'll have to mix up the body filler according to the specific brand that you're using. 
  3. Spread the body filler onto the once-rusty area using a plastic or metal spreader. You should add on an extra layer or two on top, even far above the car's paint surface, as you'll later need to sand this down.
  4. Leave the body filler for 30 or so minutes to cure and harden. Once it's dried out, use sandpaper to smooth out the body filler, matching with your car's contours and curvature. 
  5. Optionally, you could apply some rust prevention sprays to boost the corrosion resistance. But otherwise, you can fill this up by starting to repaint the car... Primer, base coat, clear coat, etc.

Treatment #3: Penetrating Rust

This is where it gets nasty, when you leave your surface, and later, scale rust goes unchecked. Initially minor cosmetic damage, it'll start eating into the metal alloy, and penetrating straight into the entire metal structure. At the very least, it'll create holes - both big and small - but at the very worst, it can weaken your car's entire frame, bodywork, and other metal components.

Penetrating rust appears when scale rust goes unfixed, and all those rusty metal flakes start chipping it away. As you can imagine, such a significant amount of rust may render your car unsafe to use. Here, you have two options for a fix...

  1. Replace the entire affected part(s) or panel(s). This is the more expensive choice, but is the less tedious as you'll only need to swap out the components. Some would argue strongly that this option is also the safer one when it comes to crash protection, by maintaining optimal structural integrity.
  2. Cut out the rusty parts altogether, and then weld "patch panels" in place. A good body shop or a professional could smoothen this out very neatly. Once repainted, you could barely tell the difference. This could prove more time-consuming but might be cheaper overall. Although, it's worth welding those panels together properly, so that your car's structural integrity is left intact. 

Conclusion - Always Be Wary...

To summarise in a pinch, treating rust on your car has a very familiar trend with almost any other automotive maintenance. Once a problem starts to appear, you would be wise to start fixing it as soon as possible, before it snowballs into something worse. Rust is no different, beginning with mere surface damage, and all the way to turn your car into a block of cheese. 

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