Condensate corrosion

An interesting and novel use of a soHd desiccant, the reduction of cold condensate corrosion in automotive exhaust systems, illustrates a hybrid closed—open system. Internal corrosion occurs in mufflers when the water vapor in the exhaust condenses after the engine is turned off and the muffler cools. Carbon dioxide dissolves in the condensate to form an acidic soup. In an essentially closed static drying step, an acid- and heat-resistant desiccant located in the muffler adsorbs water vapor from the exhaust gas as it cools to prevent formation of corrosive acidic condensate. When the engine is restarted, the system becomes open, and the desiccant is regenerated by the hot exhaust gas to be ready for the next cooldown step (19). 

Carrier gas Temperature Pressure Humidity Density Viscosity Dewpoint of all condensibles Corrosiveness Inflammability Toxicity... 

Because systems are normally not designed for use with this type of fluid, certain aspects should be reviewed with the equipment and fluid suppliers before a decision to use such fluids can be taken. These are compatibility with filters, seals, gaskets, hoses, paints and any non-ferrous metals used in the equipment. Condensation corrosion effect on ferrous metals, fluid-mixing equipment needed, control of microbial infection together with overall maintaining and control of fluid dilution and the disposal of waste fluid must also be considered. Provided such attention is paid to these designs and operating features, the cost reductions have proved very beneficial to the overall plant cost effectiveness. 

Ronchetti, C., Buzzanca, G. and Diacci, E., A New System for a Continuous Monitoring of Steam Condenser Corrosion , CISE Report, CISE-NT 81.094 (1981)... 

Alkaline gluconate programs, in cleaning processes 646 Alkaline hardness, condensate corrosion... 

The tail-gas exiting the expander at 290°C is used to preheat the high-pressure (HP) boiler feed water and also the low-pressure (LP) deionized water (prior to deaeration for high-pressure boiler-feed water use). The important design criteria in this exchanger is that the tail gas should not leave the exchanger at less than 65°C, otherwise problems with condensation/corrosion in the stack will result. The dew point of the tail-gas is approximately 17°C. 

W. Matthewman and GJ. Evans, Power Station Condensers, Corrosion Technology, 1964, 15-17. 

Figure 7.72 Schematic, showing a section of the top portion of the HPS condenser (corrosion end). (Reproduced from COM 1999 and 2005 with permission from the Metallurgy Society of CIM)...

Failure Analysis of 316 L Stainless Steel Tubing of a High-Pressure Steel Condenser Corrosion problems occurred during ammonia recovery. Figure 5.66 shows the simplified view of a high-pressure still condenser. The HPS condenser is made of 316 L seamless tubes of 25 mm diameter, 2.2 mm thick, and 6.4 in. long. The tube ends are joined to the tube sheet (100 mm thiek) to form a bundle that is welded to the shell to make up the shell-tube condenser. The tubes are weld sealed at the... 

Despite some possible implementation problems and the need for sophisticated requirenwnts for interpretation, these measurements can prove particularly valuable in low conductivity media -such as concrete, soils, condensate corrosion, protection by coatings etc. They therefore provide a more accurate determination of R. ... 

Volatilization has already been discussed under VPIs in connection with boilers and closed containers. Another application is the inhibition of gas condensate corrosion. However, the treatment here is essentially the same as used in batch or squeeze treatments (Yin 2010). 

EN 60529 does not specify sealing effectiveness against the following the risk of explosions certain types of moisture conditions, e.g., those that are produced by condensation corrosive vapors fungus vermin. 

The temperature of the system is of great importance. If the system does not become hot enough (above the dew point), the condensate remains and concentrates. Thus, vehicles, which are driven for short distances are more susceptible to corrosion by exhaust gas condensates, sometimes referred to as cold-condensate corrosion [5]. Deterioration is also accelerated by stress (both cyclic and static) and by design configurations (such as at joints and welds). 

The exhaust system and engine are exposed to a dual (external and exhaust gas) environment. Therefore, the materials must be chosen to perform in more complex service conditions. High temperatures are important along with the chemistry of the exhaust gas condensate. Corrosion mechanisms include those normal in the external environment with the additional temperature factor [S,9]. 

Assessing Materials for Exhaust Systems—Condensate Corrosion Walker Accelerated Corrosion Test Determination of Sulfur Compounds in Automotive Exhaust... 

Corrosion in mechanical pulping processes was investigated by Crowe [202] via weight loss tests and potentiody-namic polarization tests. Vapor phase condensate corrosion was more severe than liquid phase corrosion. 

Completely soluble in water and brine. Cationic behavior makes it useful for the formulation of corrosion Inhibitors. Film-forming amine. Steam volatile for boiler-condensate corrosion control. Low combining weight makes it an efficient neutralizing amine. 

Many refiners inject a small amount of caustic in the heat-exchange train downstream of their desalter. The caustic neutralizes the HCl evolved in the furnace. This is a fine way to stop condenser corrosion, but it also promotes fouling in the heat exchangers downstream of the caustic injection point. 

Crovetto R, Murtagh E. Novel boiler condensate corrosion inhibitor with FDA approval. CORROSION 2007, Paper 073. Houston, Tex. NACE International, 2007. 

CO2 is not removed by water treatment. Scales and deposits may also be formed by dissolved and suspended solids. Excessive alkalinity in boilers can lead to caustic cracking. High alkalinity is caused by high TDS (total dissolved solids) and alkaUnity. External treatment includes demineralization and reduction of alkalinity, corrosion inhibition and biological control. Morpholine inhibitor is added as inhibitor for treatment of condensate corrosion. 

---