Science of Salt Corrosion

What causes salt corrosion in coastal environments?

Salt corrosion is triggered when salt particles (like sodium chloride) from sea air combine with moisture—such as humidity, dew, or rain. This creates a thin, salty film on metal surfaces that becomes electrically conductive, initiating a process called electrolytic corrosion.

What are “electrolytic bridges”?

Electrolytic bridges are microscopic conductive pathways formed when salty moisture connects different parts of a metal surface. This film acts like a weak battery, allowing electrons to flow and triggering galvanic corrosion, a highly damaging electrochemical reaction.

What is Galvanic Corrosion?

Galvanic corrosion is a type of electrochemical corrosion that happens when two different metals come into contact in the presence of a conductive liquid—like salty moisture from coastal air.

How does Galvanic Corrosion work?

The two metals form an electrical connection (even just by touching).
Salt and moisture create a conductive bridge (like a weak electrolyte).
One metal becomes the “anode” (it corrodes), while the other becomes the “cathode” (it’s protected).

The less noble (or more reactive) metal corrodes much faster—sacrificing itself to protect the other.

Is this different from regular rust?

Yes. Rust is a simple oxidation process. Salt corrosion is electrochemical, meaning it’s powered by a reaction between metals and a conductive electrolyte (salty water). It’s faster, more aggressive, and often starts beneath the surface—invisible until damage is advanced.

Are some metals more prone to salt corrosion than others?

Absolutely! Here's a breakdown:

Highly susceptible: Aluminum, carbon steel, cast iron.
Moderately resistant: Copper, brass, bronze.
More resistant: Stainless steel (especially 316), titanium, nickel alloys.

In coastal settings, even “stainless” metals can corrode—especially in crevices or shaded areas where salty moisture lingers.