Corrosion and Water Chemistry Problems and Solutions
The following problems are frequently encountered during analyses and audits of corrosion and water chemistry control in the fossil fuel utility and industrial cycles, including combined cycles.  The following table lists the common problems under various categories, gives the root causes and possible solutions and, in parentheses, gives an estimated % of units experiencing individual problems.
Contact Jonas, Inc. for help in implementing these solutions at your site.
Problem (P.) and Root Cause (R.C.)
(% of units experiencing the problem - estimated)
 Solutions
MANAGEMENT
P. Monitoring does not prevent major water chemistry upsets
R.C. Monitoring is not round-the-clock, there are no approved actions, training, etc.  (80%)
Guidelines, training of operators and chemists, on-line instruments with alarms
P. Repeat failures
R.C. No root cause analysis - complacency (70%)
Multi-disciplinary root cause analysis, derived and verified solutions.
P. Startup delays
R.C. Water chemistry upsets, and layup corrosion during testing and commissioning of new units (90%)
Commissioning guidelines, training, corrosion protection during storage and erection.
CYCLE DESIGN
P. Difficulty in controlling corrosion and water and steam chemistry
R.C. Mixed metallurgy in feedwater system (40%)
All-ferrous systems (including auxiliary heat exchangers).
P. Difficulty in controlling corrosion and water and steam chemistry
R.C. No means to effectively remove impurities from the cycle (70%)
Boiler blowdown design, blowdown of mud drums, filtration of return condensate and feedwater, condensate polishing, frequent chemical cleaning
P. Erosion-corrosion and cavitation
R.C. High flow velocities in carbon steel piping (50%)
 Proper design velocities, use of alloy steels, reduce oxygen scavenger, increase O2.
OPERATION
P. Poor control of water chemistry
R.C. Operators underestimate the effects of upsets (60%)
 Training, guidelines, management support.
P. Wrong or delayed corrective actions
R.C. Insufficient training of operators, lack of written guidelines (60%)
Training, guidelines, management support.
P. Long startups due to high concentration of oxides
R.C. Poor startup chemistry, high oxygen concentrations (30%)
Proper layup, filling with deaerated water.
BOILER, SUPERHEATER, AND REHEATER
P. High carry-over
R.C. Damaged internals, drum level control, foaming, high solids (25%)
Inspect and fix, improve chemistry, monitor Na and cation conductivity in steam, train operators.
P. Boiler tube failures
R.C. High local heat flux and poor circulation (20%)
Adjust combustion, reduce maximum load, clean boiler, do not patch weld.
P. High water quality
R.C. High approach temperature leading to erosion-corrosion (15%)
Balance the heat input in the economizer.
P. Solid particle erosion of turbine blades and >Fe throughout the cycle, long startups
R.C. Exfoliation of magnetite (80% of other utility units)
Chemical cleaning of superheater and reheater, balancing the fireside temperatures
TURBINE
P. Blade and disk corrosion (pitting, corrosion fatigue, and stress corrosion) in the LP section
R.C. Marginal steam chemistry, no layup, high stresses and vibration (40%)
Control steam chemistry and layup, tune blade vibration, redesign blade attachment.
P. HP turbine deposits leading to loss of performance in high pressure drum boiler units
R.C. Carry-over of copper and phosphate (80%)
Optimize cycle chemistry, replace copper alloy tubing in HP heaters.
P. Sticking turbine valves
R.C. Impurities in steam (several cases of destructive overspeed) (20%)
Exercise valves weekly, improve steam purity.
CONDENSER
P. Condenser tube leaks
R.C. Many possible causes including pitting, erosion, etc. (60%)
Preventive tube plugging, replace with better material.
DEAERATOR
P. Corrosion cracking of welds
R.C. Root cause not known, possibly water piston and high residual stresses (40%)
Calculate and change the conditions for water piston, inspect periodically and perform fracture mechanics evaluation.
P. High oxygen in effluent
R.C. Distress of the internals (20%)
Fix internals, better control of pressure, temperature, and load changes.
FEEDWATER HEATERS AND HEAT EXCHANGERS
P. Erosion-corrosion of tube inlets
R.C. High local flow velocities and turbulence (50%)
Tube inlet inserts, replace tubes with more resistant material.
P. Pitting and leaks in austenitic stainless steel tubing
R.C. Presence of chloride in feedwater (30%)
Improve feedwater chemistry. When replacing tubes, use better material, test for large inclusions.
PIPING
P. Erosion-corrosion of feedwater piping
R.C. High flow velocity, turbulence, low pH, and excessive concentration of oxygen scavenger (70%)
Inspect critical components ASAP, evaluate feedwater and wet steam piping, improve water chemistry.
WATER CHEMISTRY
P. Difficulty in controlling water chemistry and detecting problems
R.C. Inadequate sampling points (i.e. steam, return condensate) (40%)
Improve sampling
P. Sampling errors
R.C. Low sample flow, high sample temperature, long sample lines, surface taps, deposits in tubing (70%)
Increase sample flow (4 to 6 ft/sec), clean coolers, satellite sampling with shorter lines, isokinetic sampling nozzles
P. High concentration of organic acids, corrosion, and scale and deposits
R.C. Inappropriate water treatment chemicals or their overfeeding (60% of industrial)
Evaluate the use of chemicals, minimize concentration, neutralize acidic conditions.
P. High concentrations of oxygen and CO2
R.C. Air inleakage (80%)
Identify locations using helium or SF6, fix leaks.
P. Incorrect analytical results from analysis of O2, SiO2, etc.
R.C. Analytical interferences due to organic chemicals (30% of industrial)
Determine interferences, change analytical method
P. Boiler tube failures: caustic gouging, hydrogen damage, pitting, and overheat
R.C. High levels of impurities in boiler water
Control condenser leaks, improve corrective actions, reduce feedwater Fe, chemically clean boiler, change water treatment
P. Contaminated return condensate
R.C. Fe, Cu, organics, process chemicals leaking into the system (40%)
Monitor, polish, automatic dump
P. Release of makeup or condensate polisher regenerants
R.C. Unreliable or poorly designed valving and inadequate monitoring (5%)
Reliable design, maintenance, monitoring, proper operator actions