Corrosion Mechanisms in Steam Power Generation
Abstract
A summary of conclusions reached in a basic research program concerned with the corrosion of steel under conditions encountered in steam power generation is given and the work done during the past year is described. This work has been concerned with: (1) The effect of OH concentration and of OH-/PO ratios on corrosion rates and on the buildup and breakdown of protective films at 600 deg F; (2) The effect of non-adherent corrosion products on the development of localized attack at 600 deg F and (3) The stabilization of protective films against breakdown upon exposure to air-saturated water at room temperature. The studies revealed that the data of Berl and van Taack, upon which conclusions regarding the beneficial effects of NaOH additions to boiler water have been based, do not give an adequate picture of these effects. Increasing the pH in static systems at 600 deg F increases the corrosion rate. The size of the crystallites in the protective film also increases with pH and this may account for increased stability of the high pH films in high velocity streams. Concentrated NaCH at 600 deg F causes drastic pitting similar in appearance to that reported by British workers as characteristic of failed high pressure boiler tubes. The attack of steel by concentrated Na2HPO4 at 600 deg F is different in character than the attack by NaOH and it does not cause the drastic pitting characteristic of NaOH. Some protection against this drastic pitting is obtained in solutions with mol ratios of NaOH to Na2HPC4 as high as 3 to 1. Concentrated LiOH does not produce this drastic pitting. The presence of non-adherent corrosion products results in drastic localized attack in highly oxygenated static systems at 600 deg F but seems to have little effect in the absence of oxygen.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1960
- Accession Number
- ADA489575
Entities
People
- G. N. Newport
- M. C. Bloom
- M. Krulfeld
- W. A. Fraser
Organizations
- United States Naval Research Laboratory