Pitting of Metals: It’s the Pits!

Metal Pitting: It's The Pits!

Corrosion can manifest itself in a number of ways.

The two most commonly used metals in firearms are steel and stainless steel. Generally, rust is the primary corrosion concern. Another common metal found in firearms – Aluminum – doesn’t rust, but it does corrode.

However, regardless of the primary metal in your firearm (steel or aluminum), Pitting is an extensive form of corrosion that should be at the forefront of gun owners’ minds.

Understanding Steel, Stainless Steel & Aluminum

Steel, stainless steel and aluminum all contain oxide layers on their outer surfaces.

Stainless Steel

Stainless SteelMany people assume that stainless steel is completely resistant to corrosion and rust…this isn’t actually the case. It’s not impervious to the caustic processes of moisture, low oxygen and salt. A more realistic way to think of stainless steel is “stains less”.

Regular Steel

SteelStainless steel differs from regular steel (carbon steel) by way of its oxide layer. Stainless steel’s outer surface contains a chromium oxide layer as opposed to carbon steel’s iron oxide layer.

The iron oxide layer of carbon steel leaves it particularly vulnerable to rust. Stainless steel’s chromium oxide layer provides vastly more effective corrosion resistance, but it’s not impervious.


AluminumContrary to steel and stainless steel, Aluminum does not rust regardless of the extremity of its environment. As mentioned above, however, it does corrode. This is due to its aluminum oxide surface layer. Aluminum oxide protects the base metal of aluminum from corrosion, however, this surface layer will deteriorate in atmospheres of high or low pH levels or when in contact with chlorides.

What is Pitting?

Metal PittingPitting is a form of extremely localized corrosion. It leads to the creation of small holes in metals… hence the name pitting!

This is a form of corrosion that literally creates visible pits in the metal, creating a rough and uneven surface.

Besides being unsightly – and usually accompanied by rust when formed on steel and stainless steel – it compromises the integrity of your metal and can lead to substantial degradation.

What Causes Pitting?

There’s a variety of ways in which pitting can be initiated.

The primary cause of the development of pitting is localized chemical or mechanical damage to a metal’s protective film. This refers to the differences in the metals emphasized above:

  • Stainless Steel’s Chromium Oxide Layer
  • Steel’s Iron Oxide Layer
  • Aluminum’s Aluminum Oxide Layer

Another common way in which pitting forms is through poor or improper coating techniques. If a coating is applied unevenly, the metal will contain areas in which it’s particularly vulnerable to corrosion. These areas will be the first to go if contained within an environment high in humidity or salinity.

In turn, the pitting will begin to spread to areas surrounding the origin site. As a metal’s oxide layers begin to breakdown, corrosives come in contact with the base metal. As they eat away at the metals surface, small holes are formed.

How to Fix Pitting

Abrasive Sand Paper There’s only one way to fix metal pitting…sanding and/or abrasion. Pitting isn’t like other forms of corrosion that can be dealt with via chemical treatment.

Because pitting physically eats away at the metal and leaves cavities, the only solution is to sand down the pitted area on the metal entirely. Once the pitted holes are sanded out and the surface area of the metal is even, a new coating could be applied. As you may have guessed, sanding and abrasion isn’t always an option.

In terms of pitting on firearms, there are a few reasons why you wouldn’t want to sand down your gun:


Whether your firearms are antiques, collectables or more contemporary, sanding down your gun barrel often results in depreciation of the weapon’s value. Ever seen an episode of Antique’s Roadshow? If so, you might notice the devastating effects on price and quality that result from improper repairs.

Uneven Coating

More often than not, pitting on a firearm is localized – usually it’s not spread throughout the entirety of the gun barrel. This means a section of the gun is pitted and a section is in good/fair condition.

If you elect to sand down the pitted area of the weapon and re-coat it with some sort of corrosion protection, this can result in an uneven coating. Furthermore, if the new coating differs from the originally coating, more issues may arise.

Proactivity Prevents Pitting

The best way to handle the effects of pitting? Don’t let it happen in the first place!

How Our Proprietary Intercept Technology Works

Check Out Our Gun Bags to Ensure That You’re Never in the Pits!

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