Effects of oxygen, copper and acid chlorides on denting corrosion
The effect of dissolved oxygen and copper on denting corrosion at 280/sup 0/C in solutions of NaCl at pH 9 with ammonia was investigated using a packed tube/support plate crevice in a laboratory simulation. The onset of corrosion was detected with a hydrogen analyzer sensitive to 0.2 ppB. In the absence of copper, rapidly rising hydrogen concentrations were detected only when the product of the chloride and oxygen concentrations were detected only when the product of the chloride and oxygen concentrations in the boiler-water exceeded 25 (ppM)/sup 2/, but at these high concentrations, unheated low-carbon steel surfaces in the system were as sensitive to corrosion as the heated crevice. When copper metal was present in the feed system, corrosion of the heated crevice occurred in the absence of oxygen, provided the copper had previously been exposed to dissolved oxygen. Dosing hydrazine into the feedwater eventually suppressed the ability of copper to initiate corrosion. It is proposed that copper ions are more efficient than oxygen in promoting corrosion within the crevice because unlike oxygen thay are carried into the crevice during boiling. Corrosion results from the anodic formation of acidic solutions in the crevice as a result of the cathodic reduction of oxidized copper species. 20 figs.
- Research Organization:
- Central Electricity Research Labs., Leatherhead (UK)
- OSTI ID:
- 5508490
- Report Number(s):
- EPRI-NP-4648; ON: TI86920406
- Country of Publication:
- United States
- Language:
- English
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36 MATERIALS SCIENCE
360105 -- Metals & Alloys-- Corrosion & Erosion
ACID HALIDES
ALLOYS
BOILERS
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
COPPER ALLOYS
CORROSION
CORROSION INHIBITORS
CREVICE CORROSION
ELEMENTS
HALIDES
HALOGEN COMPOUNDS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXYGEN
PWR TYPE REACTORS
REACTORS
STEAM GENERATORS
TUBES
VAPOR GENERATORS
WATER COOLED REACTORS
WATER MODERATED REACTORS