Does stainless steel pipe rust?

Stainless steel is known for its resistance to rust and corrosion, but under certain conditions, it can still experience corrosion. Stainless steel contains a minimum of 10.5% chromium, which forms a thin, invisible layer of chromium oxide on the surface. This layer, called the passive layer, protects the underlying steel from rusting.

However, if the passive layer is damaged or compromised, the stainless steel can become vulnerable to rusting. Factors that can lead to the breakdown of the passive layer and rusting include:

1. Exposure to corrosive environments: Stainless steel can be affected by certain corrosive substances like chlorides, acids, and salts. For example, if stainless steel pipes are exposed to high levels of chloride ions, such as in coastal areas or environments with high salinity, pitting corrosion or crevice corrosion may occur.

2. Mechanical damage: Scratches, gouges, or other forms of mechanical damage to the surface can disrupt the passive layer and provide a pathway for corrosion to start.

3. Lack of oxygen: Stainless steel requires oxygen to maintain the passive layer. In environments with limited oxygen supply, such as stagnant water or buried applications, stainless steel may be more prone to localized corrosion.

4. Extreme temperatures: In some cases, exposure to very high temperatures can lead to the formation of chromium carbides, which can deplete the chromium content near the grain boundaries and cause intergranular corrosion.

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