- [Alex] In this episode of Out Of Our Elements, we're on the hunt for a destructive force of calamitous chemistry: RUST.

- You start to create a chemical reaction with the corrosion, then it starts to infect that panels and spread.

- [Alex] And there's more.

This conniving chemical creation's causing billions of dollars in corrosion in our locomotives, automobiles, pipes, and planes.

And the car of our determined detective.

If only there was a team that could solve this mystery.

- I have a big problem.

My car is over 30 years old, it's almost as old as I am.

(camera clicking) I recently had it sanded and repainted, but now there's this crusty spot that's come back, and I'm trying to figure out how.

- I think your car is under attack from a rust problem.

Hmm, we got this.

- Hey Alex!

This is what you call me in for?

- Yeah.

- That tiny thing right there?

♪ It's very tiny ♪ - I understand the rust on my car isn't a big deal, but it's not just an issue for my car.

The bigger picture is that pipes, our roads, our bridges, all of it has metal in it.

Corrosion isn't just annoying, it could be dangerous.

- Let's do it, but we should probably call Caitlin.

- I've got the download on rust and get this: Rusting is actually like a very slow burn.

It even gives off a tiny bit of heat.

So when something combusts, one substance is transferring electrons to molecular oxygen to form some other oxygen-containing compound.

Rusting is a similar process, but with iron or one of its alloys.

- Wait, what's an alloy?

- It's like a mixture of metals.

So when iron is exposed to water and oxygen, the iron loses electrons.

We say the iron is oxidized, the oxygen is reduced because it gains those electrons, making it more negatively charged.

This oxygen-reduction reaction or redox reaction forms what we see as rust.

But it can take a really long time under certain conditions.

However, it goes faster if there's an electrolyte solution.

- Wait, electrolytes, like in Gatorade?

- Or any fluid that contains ions that help electrons move.

Water is the most common.

Even the water present in the atmosphere is enough to begin the process of rusting.

The electrolyte acts like an accelerant.

If you add more electrolytes to the water, like add more salt for example, it's like kerosene on a fire pit, and accelerates the chemical reaction.

- [Alex] The Interstate Highway System we're driving on was authorized in 1956, and many high-use bridges were produced in the following two decades.

It's a good reminder of how ancient much of our infrastructure is.

Steel pipes, for example, became commonly used in the late 19th century.

And that's about the time we started protecting steel with coatings such as zinc, to slow the rusting process.

Zinc acts like a sacrificial barrier between the steel and the oxygen in the environment.

The exposed zinc transfers more of its electrons, while the metal beneath remains protected for longer.

Many cars have protective coatings, but they don't last forever.

So let's see what happens when corrosion reaches the metal beneath.

- We made it.

- So I am Jo Izzo, and I am one of the managers here at J.B.

Body works.

It's my family business.

It's an Auto Body shop.

And we've been in business since 1982.

- [Alex] I wanna learn more about how to slow rusting, and repair its damage.

But first, we need to understand how rust happens, specifically in cars.

- I used to live in LA and it was perfectly fine there.

And then I moved to the Northeast, and started getting all these rust problems.

Why is that?

- Yeah.

So because of all the snow that we have and the inclement weather, we use a lot of salt to kind of keep the roads clean and clear of any ice.

This salt acts like an electrolyte, which begins the chemical catalyst that creates the breakdown and ultimately cause of the rust.

So if you come over here, you can see that this is an area that's been very much effected by the rust.

You can see it's rotted through and there's a gaping hole.

At the bottom, which is completely exposed to the elements.

- [Alex] Repairing something like this beautiful Mercedes could cost thousands of dollars.

And just as Caitlin concluded from her investigation, electrolytes contribute heavily to the formation of rust and living in the Northeast.

My car is subjected to an environment that promotes decay.

So what can I do about it?

- So when rust hits a certain level, it'll start to deteriorate the metal entirely and you'll get big holes, and metal will become very brittle, and it'll fall apart at the touch.

So at that point, our best bet is to cut out the infected area until you reach a point where there's no rust or rot at all.

Fabricate a new piece, weld that piece in.

- So what Jo's really saying here is there's no such thing as rust repair.

It's more like removal and panel replacement because you can't reverse the process.

I started noticing rust spots on the roof, so I get it repaired.

They sanded it, they primed it, they painted it.

I called Arlo to come up and take a look at it because I actually discovered a couple of spots.

- Yeah, it looks like you can see the corrosion coming through, through the bare substrate up and through the paint.

So a lot of times, if you don't completely remove the rusted area, you'll still have that breakdown.

You'll still have that exposure, those electrolytes, that chemical process is still going on.

It's growing.

So unless you cut that out and fab in a new piece, it's very difficult to entirely remove the rust.

A lot of times it comes back.

- [Alex] So if you haven't figured it out, I'm starting to hate rust.

It's not fully preventable and it attacks our valuables.

So what is the answer?

Are protective coatings enough to sustain infrastructure that will someday fail?

- The coating, it's important to use.

And that's one of the most, or the most used prevention ways of corrosion.

We have infrastructure of 1900s.

We been having some accidents due to corrosion that costs lives.

And that's what we cannot afford.

- [Alex] Infrastructure is designed like cars, with the understanding that someday, everything will have to be repaired or replaced.

So engineers often have to balance price with safety.

- In perspective, rust can help us as an indicator.

You need to set a parameter that indicates this is the time that we need to replace.

This is the threshold.

This is the point.

This is a range that we need to replace.

And that will be more cost effective long-term.

- [Arlo] I found an interesting example of this.

What happens when structural damage from rust and the environment hits those crucial levels?

So this is actually an example of what rust can do to a bridge.

This bridge was too rusty for vehicles to go on it, and later on, it was too rusty for people to go on it.

So right now they just kind of turned this bridge into an island.

- So through this journey I learned that rust is something society has battled with for hundreds of years.

- It seems like the challenge facing our infrastructure are results of the age of the materials and the environment.

Corrosion like rust is simply inevitable.

- So there are solutions based in chemistry, like coatings that protect metal.

- But there's always going to be a need to monitor and create guidelines for when repairs are needed.

- Replacing, repairing, it has to be with knowledge.

- Rust isn't new, but with so many structures nearing the end of their life, it's impact is more important than ever.

If we're as vigilant as you are with your car, we should be all right.

- [Alex] And of course, rebuilding and replacing materials that are constantly in a state of failing takes money.

Infrastructure repairs is something governments have tried to tackle for years.

- Our economy depends on us having the most efficient, reliable transportation system in the world.

- So we have to build roads.

We have to build highways.

We're talking about a very major infrastructure bill.

- [Alex] It seems like, in America at least, we're closer than ever to big investments in our infrastructure.

- We're on the cusp of an infrastructure decade that I truly believe will transform America.

- [Alex] But time will tell if it makes a difference.

- Does the leaning down to the camera good?

- [Woman] Yes.

- Okay.

Now it's just kind of an island in the middle of the whole thing.

- [Woman] Okay, now it isn't focused.

- Now it isn't focused?

Okay.

Let me come back into it.