Accession Number : ADA330947

Title :   Corrosion Consequences of Molten Salt Deposits in Combustion Turbines Burning Vanadium Contaminated Liquid Fuel, Tri-Service Conference on Corrosion Proceedings

Corporate Author : NAVAL SURFACE WARFARE CENTER CARDEROCK DIV ANNAPOLIS MD

Personal Author(s) : Rathnamma, Dasara V. ; Nagarajan, R.

PDF Url : ADA330947

Report Date : JUN 1994

Pagination or Media Count : 36

Abstract : Molten salts condensing on marine turbine blades can dissolve the protective oxide coating and catastrophically attack the exposed alloy surface beneath-- a process known as hot corrosion. We present here the implications of a theoretical model of hot corrosion rate that is limited by diffusional dissolution of oxide species into the melt for the design of burner-rigs to test the corrosion-resistance of superalloy materials. Parameters expected to govern the dissolution rate of a given oxide are the rate of deposition of the multicomponent(sulfate-vanadate-oxide)'solvent'- liquid, liquid-layer thickness, and composition-dependent physical properties of the deposit, such as density and viscosity. The solid portion of deposit mass, being relatively inert with respect to hot corrosion, will not correlate well with experimental corrosion rates. These hypotheses are tested by comparing our model-predictions with one set of burner-rig corrosion rate measurements made during the combustion of vanadium-containing liquid fuel seeded with the same concentration of various metallic additives. Our findings indicate that the total weight (solids + liquid) of the deposit has no direct correspondence with its corrosive potential. However, additives that are effective in suppressing liquid phase formation will, in general, reduce the corrosion rate equally effectively. Liquid mass arrival rate and oxide solubility in the liquid are quantities of relevance to the problem, but the best correlation of experimental data with theory is obtained for the oxide dissolution rate (which is approximately inversely proportional to the liquid layer thickness). Thus, burner-rigs designed to simulate either of these two parameters will reproduce the hot-corrosion characteristics of the engine with reasonable accuracy.

Descriptors :   *COMBUSTION, *DEPOSITS, *FUELS, *CORROSION RESISTANCE, *TURBINES, *VANADIUM, *MOLTEN SALTS, MATHEMATICAL MODELS, METALS, MEASUREMENT, EXPERIMENTAL DATA, SYMPOSIA, LAYERS, MATERIALS, HIGH TEMPERATURE, MELTS, SOLIDS, TURBINE BLADES, LIQUID PHASES, OXIDES, JOINT MILITARY ACTIVITIES, PROTECTIVE COATINGS, ADDITIVES, SULFATES, CONTAMINATION, SOLUBILITY, VISCOSITY, BURNERS, SUPERALLOYS, VANADATES, MARINE ENGINES.

Subject Categories : Properties of Metals and Alloys
      Marine Engineering

Distribution Statement : APPROVED FOR PUBLIC RELEASE