Definition - What does Denickelification mean?
Denickelification is type of corrosion in which nickel is selectively leached from nickel-containing alloys. It is most commonly observed in copper-nickel alloys after extended service in fresh water or sea water. It can be observed in 70/30 copper-nickel alloys both in severe and less severe conditions.
The severe form of denickelification is known as hot spot corrosion. This type of attack can be prevented by continuous flow of sea water, installing anodes and relocating the unit.
Corrosionpedia explains Denickelification
Cupronickel pipes are widely used in cooling systems, and denickelification of cupronickel tubing is a common occurrence in the heat exchangers that use these tubes. The primary cause of waterside failure of cupronickel (70/30) condenser tubes was identified as plug-type denickelification. This corrosion phenomenon involves the creation of an active corrosion cell that dissolves the alloy and then redeposits the copper back on the surface. Once the denickelification is started, it can be self-propagating because oxygen access to the pit environment is limited.
Denickelification is sometimes reported in the higher-nickel content copper-nickel alloys in refinery overhead-condenser service, where hydrocarbon streams condense at temperatures above 300°F (149°C). The problem appears to be associated with hot spots that develop in the tubing as a result of fouling and thermogalvanic differences that arise.
Although extensive studies have not been undertaken, the solution is more frequently cleaning to remove deposits that can lead to hot spots and/or increasing flow rate to avoid deposits.