Stages of Rust on Iron Nails

Rust accumulates on nails that get wet and are exposed to oxygen over time.rusty nail image by Yali Shi from Fotolia.com

Rust on iron nails goes through three basic stages of rust discoloration and corrosion before falling apart completely. This occurs when nails are in a moist environment for an extended time while also exposed to the air. Rusty nails carry tetanus and should be removed and disposed of in trashcans so no one can step on them.

Stage 1

There are the initial signs of discoloration on the nail in stage one. This consists of red, black and white corrosion deposits along the surface of the metal. There will also be a bit of etching and pitting from the rust as the outside of iron begins to break apart due to reduction of the water and oxygen of the metal to hydroxide ions. However, the core metal strength of the metal is still sound and strong.

In the second stage of rust on an iron nail, oxidation continues and the electrochemical process continues, causing even more corrosion on the surface of the metal, like a lesion spreading. A powdered, granular and scaly condition results along the smooth metal surface. While the iron itself is still eroding, the base metal is still sound, meaning the nail has strength and will hold as it should in a structure.

The third stage of iron nail rust has a continuation of the conditions in Stage 2, with the surface becoming increasingly corroded, flaky and powdery. Stage 3 begins when the corrosion reaches a certain point and a certain amount of weakness actually occurs to the iron nail itself. This weakness occurs in the corroded areas, where small pinholes may be present, meaning the iron has rusted straight through.

In Stage 4 of iron nail rust corrosion, the surface of the nail itself is almost entirely corroded in some way, having changed colors and comes off in flakes or powder. The entire surface of the iron nail has been entirely penetrated and the core strength of the nail itself is disintegrating more and more quickly. At the points of severest corrosion no metal remains at all. There are rust holes everywhere and the basic structure of the nail itself is compromised and can break with a small amount of pressure.