Corrosion in submersible pumps and what to do about it

When getting your submersible water pump rental, you can be worried about corrosion. The risk of corrosion in submersible pumps is determined by the environment the pump is exposed to and the medium that the pump is required to pump. Some of the common liquids that pose a risk of corrosion include hydrochloric acid, seawater, and some types of hydrogen sulphide , solvents, bases with high pH, liquids with a high copper content and some liquids that contain a mixture of acids. With metals, it is normally the case that substances that have a high concentration of corrosive substances pose a worse risk of corrosion. For plastics and rubber, long term exposure to low concentrations can result in severe corrosion.

Counteractive strategies

In submersible pumps, there are two basic ways to counteract corrosion. The first method is to have the entire pump manufactured from a corrosion-resistant material. The second method is to utilize other measures such as anodes, coatings, or/and the use of resistant materials for certain components that are exposed to a risk of corrosion.

When you look at the main material of pump manufacture, you will realize that most submersible pump operations are done by cast-iron pumps. This presents no corrosion problems when it comes to pumping liquids like domestic sewage and surface water. The low oxygen in raw sewage reduces its corrosion effect to nearly nothing. When it comes to construction and mining applications, aluminium waterwell pumps are usually preferred. This is normally for weight reasons since most of these pumps are portable and not for matters to do with corrosion. The main pumps in mining sites, on the other hand, are made of cast iron. Cast iron is a robust and cheap material and these pumps are normally stationary. This means that weight considerations are not very important.

Stainless steel

This material is used as the main construction material to make submersible pumps for two reasons: the first reason is for use in acidic liquids and the second reason is where the purity of the liquid being pumped is of important consideration as in some process industries such as paint and paper production companies where colour purity is crucial.

Coating and anodes

This is a cheaper and more flexible alternative that can withstand saltwater corrosion. This is where a coating is used on cast iron pumps. This is a more flexible alternative because the range of Flygt pumps can be easily coated. The most common coating used is epoxy. Zinc anodes are usually used in conjunction with epoxy coating because of the inevitability of post-production scratching that occurs in the coating.

Using anodes extends the life of a coated submersible water pump rental. Between 5 and 10 anodes are implanted at different points around the cast iron material or structure of the pump. Zinc has a lower electric potential compared to cast iron and this means that the contact between the two materials generates a micro-current. The current protects areas of cast iron that are exposed by the scratches and zinc anodes are corroded.

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