The most common and internationally approved alkalization additive is ammonium hydroxide. The use of this chemical additive for buffering cycle pH’s has no degradation products and offers limited cycle chemistry related risks. Care however should be taken when applying ammonia for alkalization in mixed metallurgy installations when residual oxygen could be present.
Ammonia readily reacts with oxidized copper. The complex formed increases corrosion and may accompany “ammonia grooving”.
Ammonia is the most common conditioning agent in the steam/water cycle. Due to its volatility and relatively weak dissociation, it provides only moderate alkalization in the liquid films in the turbine to counteract anionic impurities. Care should be taken to avoid impurities in chemicals added to the cycle, including ammonia, as these could be a source of chloride, sulfate etc.
The use of neutralizing or alkalizing amines offers chemical additives with highly reactive functionality. Apart from their undesirable direct reaction with and subsequent removal of the protective copper
hydroxide patina, their degradation products are organic acids which increase the risk of non-compliance, high CACE measurements and increased threat of oxide related organic acid chelant based corrosion.
“Amines. Selected amines such as cyclohexylamine, morpholine, ethanolamine and others offer the possibility of greater partitioning into the liquid phase in the phase transition zone, as well as stronger alkalization, and thus perhaps better corrosion protection of turbine components. However, the balance of alkalization between amine and its possible acidic decomposition products must be considered”
“Plants where the preferred water treatment is based on organic additives as well as plants where the use of organic additives is due to outsourcing of the management of water and steam chemistry to chemical vendors, either to save the cost for chemists or because of a lack of qualified chemists. Thermal decomposition of such organic additives often results in high steam CACE”. (1)
Anodamine does not change the cycle pH and has no appreciable effect on measured conductivities. With Anodamine, ammonium hydroxide is the recommended alkalization and pH-buffering additive. In comparison, conventional film-forming amines are required to use neutralizing amines for solubility issues, in a multi-component mixture. The end result is a huge limitation on separation between pH control and metal protection.