PB Blaster Rust Penetrant Compared to WD-40

PB Blaster Rust Penetrant Compared to WD-40: What’s Really in the Can?

I’ve freed more rusted bolts than I can count, and over the years, I’ve tested just about every product on the shelf. One of the most common questions I hear is: “Is WD-40 the same as a rust penetrant like PB Blaster?” The short answer is no, not even close in my opinion. But to understand why, you have to take a closer look at what’s inside these products and what makes one better than the other when you’re dealing with corrosion.

In this article, I’ll break down the ingredients in WD-40 compared to rust penetrants like PB Blaster, explain how they work, and tell you what to use when you’re staring down a frozen fastener that just won’t budge.

What Makes a Good Rust Penetrant?

To be truly effective, a rust penetrant needs several characteristics:

• Low viscosity – It must creep into microscopic gaps between threads.
• Surface tension modifiers – These allow the liquid to spread and wick into corrosion layers.
• Chemical rust breakdown agents – Mild acids, chelators, or esters help dissolve iron oxide.
• Lubricating oils – Once the rust is broken, they reduce friction and aid turning.
• Corrosion inhibitors – These protect the metal after the bolt is removed.

This is exactly what makes PB Blaster a better product when comparing WD-40 compared to rust penetrants like PB Blaster. It checks every box for what a rust penetrant should do, while WD-40 does only one or two.

What’s Inside WD-40 Compared to Rust Penetrants Like PB Blaster?

Most people recognize WD-40 by its signature blue and yellow can. It’s a household name and one of the most versatile sprays ever made. But when we’re comparing WD-40 to rust penetrants like PB Blaster, it’s important to know what’s actually in them.

WD-40 contains:

• Aliphatic hydrocarbons (decane, nonane) – These are light solvents that evaporate quickly and help the product penetrate tight spaces.
• Petroleum base oils – Provide light lubrication and leave a protective film.
• Hydrotreated heavy naphtha – Another petroleum solvent that displaces moisture.
• Carbon dioxide – Acts as a propellant in the aerosol can.

These ingredients make WD-40 great for displacing water, loosening light grime, and lubricating lightly stuck parts. But they don’t chemically break down rust.

What’s Different About a Real Rust Penetrant Like PB Blaster or Knock’ER Loose

On the other hand, PB Blaster is designed to be a rust penetrant from the ground up. Its formula typically includes:

• Petroleum distillates (Stoddard solvent) 60%-70% – Thicker and more aggressive than WD-40’s solvents.
• Hydrotreated Light Petroleum Oil 15–25%—  Provides lubrication after solvent evaporates; leaves a protective film
Lubricating Oil Additives (proprietary) <10%— Improve rust penetration, lubrication, and corrosion resistance
Corrosion Inhibitors / Surfactants / Esters Proprietary Trace–5%— Surfactants or citric acid derivatives – These help break the bond between rusted surfaces and help the formula creep deeply into corroded threads. Anti-corrosion additives prevent future rust after the fastener is freed
Fragrance Proprietary Trace Mask odor— no functional mechanical effect
Carbon Dioxide (CO₂) <5%—  Propellant in aerosol cans

I prefer PB Blaster or Kroil but I’ve also used Knock’r loose

Why PB Blaster Penetrates Rust Better Than WD-40

When you’re dealing with rusted bolts, you need more than just a light oil—you need chemistry that actively breaks down iron oxide (rust). That’s where PB Blaster and other dedicated penetrants shine.

WD-40 compared to rust penetrants like PB Blaster falls short in one key area: chemical action. While WD-40 is excellent at water displacement and offers some lubrication, it doesn’t contain acidic or chelating agents that attack rust. PB Blaster includes surfactants and possibly weak acids or esters that actively soften the corrosion layer between threads.

In practical terms, that means PB Blaster can soak into a rusted joint, weaken the bond at a molecular level, and make it easier to turn the bolt. While WD-40 might help a mildly seized bolt, it doesn’t work well on a truly rusted fastener; you’re better off reaching for a real penetrant.

WD-40 Compared to Rust Penetrants Like PB Blaster in Real-World Use

Over the years, I’ve found that people often misuse WD-40, thinking it’s a cure-all. But when it comes to WD-40 compared to rust penetrants like PB Blaster, context is everything. Here’s how they stack up in different situations:

My Choice is Always PB Blaster, Kroil, Knock’ER Loose, or Freeze-Off instead of WD-40

If I had to choose just one for general shop use, I’d still keep both cans on the shelf. WD-40 is great for cleaning, displacing water, and protecting tools, but it’s not the right tool for rusted hardware.

When it comes to penetrating rust, PB Blaster wins hands down. It has stronger solvents, deeper penetration, and ingredients designed specifically to break the molecular grip that rust holds over metal fasteners.

So the next time you’re facing a stuck bolt, don’t reach for WD-40 out of habit. Think about the chemistry, and you’ll understand why WD-40 compared to rust penetrants like PB Blaster is like comparing a screwdriver to an impact wrench—they both have their place, but only one is meant to do the heavy lifting when rust gets in the way.

©, 2025 Rick Muscoplat