Flow-Assisted Corrosion (FAC) related failures typically result in catastrophic equipment failures and the possibility of human fatalities. This debilitating mechanism has garnered a huge awareness across the international community. There is a lot of excellent published work by both EPRI, IAPWS and many others on the FAC mechanism and mitigation of the same.
An initial simplistic approach would be to look at FAC both in the single and 2-phase locations, the basic differences between the mechanism at different locations in the steam water cycle, the effects of temperature, pH, flow geometry, oxide morphology and the drivers that affect magnetite solubility and the chemistry challenges to control FAC at these different plant locations.
The Anodamine surface active film forming metal protection mechanism importantly commences initially, rapid isolation of the anode (virgin base metal), then accompanies a slow and progressive cycle clearance and stabilization of the existing oxides. Please see stages of protection.
The Anodamine treatment and protection mechanism may not initially accompany an immediate reduction in oxide transport, this is because the film formation and anode isolation occurs first at the virgin metal protective oxide interface. However, with continued treatment and exposure, oxides are progressively freed of inorganic contaminants (cycle clearance) and the stability, resilience and hydrophobicity of the oxides are significantly improved. All these factors appreciably lower the risk of FAC both in the single and 2-phase locations.
Like oxygen, ammonium hydroxide has a very low solubility in high temperature liquid. Like the desired presence of oxygen, both tend to thermally deaerate out of the liquid film, leaving pH control and the full and very desirable oxidizing power of residual oxygen of minimal benefit for formation of the more desired hematite based protective oxide.
Since the Anodamine treatment has an approximately 60 % volatile, 40 % non-volatile partition ratio (see section 60/40 Volatile to Liquid Ratio), protection from FAC occurs both in single, two-phase and all liquid film locations. This unique protection from FAC related damage, oxide transport, tube wall thinning and re-deposition of corrosion products is especially evident where conventional chemistries simply fall short.
Some useful information on FAC can be sourced by searching for published data, a few important publications are as follows: