O₂ dissolved in water is one of the primary causes of corrosion in the oil field. When O₂ is present, the most common types of corrosion include pitting corrosion and uniform corrosion occurs. Crevice corrosion and pitting corrosion are related because they both require stagnant water, chloride, and oO₂ or CO₂. The mechanism of corrosion is very similar for both. O₂ is a strongly reacts with metal. The maximum amount of O₂ in water is only 8 ppm, so the mass transport of oxygen is the rate limiting step in oxygenated non-acidic environments.

 
Oxygen Pitting Corrosion

Controlling the rate of oxygen transport (often by controlling flow velocity) is thus critical to corrosion control.
O₂ corrosion products include iron oxides, including FeO(OH)- goethite, Fe₂O₃- hematite,Fe₃O₃ - magnetite, and FeO(OH) - ferrous hydroxide.

Although it is not normally present at depths below around 330 ft (100 m), oxygen is often introduced in oil production through leaking pump seals, casing and process vents, open hatches, and open handling. In addition, oxygen removal processes such as gas stripping and chemical scavenging often fail, allowing oxygen contamination in waterflood systems.

O₂ corrosion occurs commonly in drilling fluid, primary production in rod pumped wells, outdoor rod storage (rusting), oxygen entry into wellbore through annulus, lower part of well including casing, pump, tubing, lower part of rod string

Prevention

Oxygen removal may be done by mechanical include gas stripping and vacuum deaeration; and chemical means include sodium sulfite, ammonium bisulfite and sulfur dioxide. Mechanical means of oxygen removal are usually employed when large quantities of oxygen need to be removed, while chemical means are used to remove small quantities of oxygen and may be used to remove residual oxygen after mechanical means have been used.

It is often more economical to exclude O₂ from oilfield equipment than to remove it after it has entered the system. The most common way of excluding oxygen is through the use of gas blankets, composed of oxygen free gas such as natural gas (methane) or nitrogen. Gas blankets may be used on water supply wells and water storage tanks, supply wells and producing wells, and pumps. Most tanks only require a few ounces of pressure. The regulator should supply gas at a rate adequate to maintain pressure when the fluid level drops. Maintenance of valve stems and pump packing is also important.

To reduce or prevent corrosion in an O₂ environment

• Drilling - O₂ scavengers
• Producing wells - corrosion inhibitors, oxygen scavengers, elimination of O₂ sources
• Flowlines - corrosion inhibitors, oxygen scavengers, elimination of O₂ sources