Corrosion takes place due to chemical reaction with oxygen. While this applies to most materials, nearly all metals will eventually lose strength and malleability while decomposing to metal oxides. Iron, for example, inevitably reacts with air and moisture to form iron oxide – rust.
Inevitable decay is a problem to our metallic structures and equipment. Effort has been made in the past to develop corrosion-resistant materials like stainless or galvanized steel, or chemical and other surface treatments such as paints and polymers.
Corrosion of building materials represents a safety hazard, while corrosion has an economic impact measured in hundreds of millions of dollars annually. There are safety, and toxicity issues related to heavy metals and leaking industrial compounds, including the hydrocarbons of the fuel industry. Certain metals have negative health effects. Heavy metals in the environment occur from nearly all metal-using industries, but particularly from metal mining and smelting operations, as well as metallic waste.
But the oxides of these metals formed by corrosion are more stable and occur naturally.
Corrosion can occur as a result of contaminations. Microbiological corrosion occurs when colonies of bacteria develop on a surface, known as a “biofilm”. While the bacteria itself does not do damage, the waste products which they secrete can – this is known as “induced” corrosion. There is also chemically-induced corrosion resulting from exposure to substances like sodium hydroxide or methanol. This occurs because oxygen is much more soluble in methanol than water, and corrosion is accelerated. This is a problem in the oil and gas industries where localized corrosion leads to pipeline leaks.
It is thus possible to induce corrosion with these agents. In some cases, as with aluminum, titanium, chromium, or zinc alloys, a hard outer layer of oxidation prevents further deterioration of the underlying metal. This is why stainless steel, made with chromium, is more resistant than ordinary steel. Strong alkaloids applied to certain metals such as cadmium have the same effect.
Bearing this in mind, inducing corrosion in such materials can actually help preserve them. In common iron alloys, it can accelerate disposal of non-reclaimed scrap which otherwise might lie intact for decades. It can also benefit concrete structures, where some level of corrosion is needed to bind the concrete to otherwise smooth steel. Concrete made with magnesium oxides is better than traditional cement for the environment, releasing much less carbon dioxide during manufacturing.
Metal oxides are known to immobilize arsenic in contaminated mining sites. Induced corrosion is also beneficial in the destruction of nuclear wastes, which includes quantities of carbon steels. Corrosion is typically low in deep ground water environments, but microbial corrosion has an enhanced effect on the biodiversity of the surroundings.