Condensation Corrosion in Movile Cave, Romania, 1997, Sarbu, S. M. , Lascu, C.

Condensation corrosion is the dissolution of carbonate by acidic vapors condensing above the water table. This process is rarely noted and receives little attention in the mainstream cave literature. The oolitic limestone walls in Movile Cave’s upper dry passages are severely altered by a selective corrosion mechanism. Temperature differences between the water in the lower passages and the walls in the upper passages and high concentrations of CO2 in the cave atmosphere create favorable conditions for condensation corrosion to take place. Carbon and oxygen stable isotope data support the hypothesis that condensation corrosion is the major mechanism currently affecting the morphology of Movile Cave’s upper dry level.

The Problem of Condensation in Karst Studies, 1998, Dublyansky, V. N.

Condensation in karst occurs over a wide range of natural settings, at latitudes from 25º to 70º and altitudes from sea level to 2600 m. In summer (April through September), condensation introduces a significant amount of water into the karst massifs (from 0.1% to as much as 20% of the total dry-season runoff). Contrary to common belief, in winter evaporation does not withdraw appreciable amounts of water from the massifs. Evaporating at depth, the water condenses near the surface within the epikarstic zone or on the snow cover and flows back. Condensation can sustain springs during prolonged dry periods (such as summer and winter) when there is no recharge by liquid precipitation. Condensation can play a significant role in speleogenesis, and many forms of cave macro-, meso-, and micromorphologies are attributable to condensation corrosion. It can be particularly efficient in the latter stages of hydrothermal cave development (during partial dewatering) when the temperature and the humidity gradients are highest. Coupled with evaporation, air convection, and aerosol mass transfer, condensation can play a crucial role in the formation of a number of speleothems, as well as create peculiar patterns of cave microclimate.

Condensation Corrosion in Caves on Cayman Brac and Isla de Mona, 1998, Tarhulelips, R. F. A. , Ford, D. C.

Many speleothems in caves on Cayman Brac and Isla de Mona have suffered considerable dissolution. It is suggested that this is a consequence of condensation corrosion rather than of aqueous flooding of the entire cave. A program of temperature and relative humidity measurements during the rainy seasons showed that the entrance zones are areas of comparatively large diurnal variation where condensation from warm air onto cooler walls may occur. Artificial condensation was induced using ice bottles: chemical analysis of the condensation waters determined that they were generally undersaturated with respect to calcite and/or dolomite but that this changes over space and time. Gypsum tablets were suspended inside three sample caves on Cayman Brac and one on Isla de Mona for 16 and 13 months, respectively. At the end of this period, tablets close to the entrances and to the floor were found to have undergone considerable dissolution; this could only have been the result of condensation corrosion

Karst processes on Cayman Brac, a small oceanic carbonate island, PhD Thesis, 1999, Tarhulelips, Rozemarijn Frederike Antoinette

Cayman Brac is a good example of a small oceanic carbonate island which has undergone several periods of submergence and emergence since the Tertiary, resulting in the geological formations being well karstified. This study investigated several karst phenomena on the island including the occurrence and morphology of caves, the water chemistry and microclimate inside the caves, periods of speleothem growth and dissolution, and bell holes. Caves occur throughout the island at various elevations above sea level. Using elevation as a criterion, the caves were divided into Notch caves, located at, or one-two metres above, the Sangamon Notch, and Upper caves, located at varying elevations above the Notch. Analysis of the morphology, age and the relative abundance of speleothem in the caves further supports this division. The close proximity of the Notch and the Notch caves is coincidental: speleothem dating by U-series methods shows that the caves predate the Notch. They are believed to have formed between 1400 and 400 ka, whereas a late Tertiary to Early Quaternary age is assigned to the Upper caves. Speleothem on the island has suffered minor, moderate and major dissolution. Minor dissolution is due to a change in the degree of saturation of the drip water feeding the speleothem, whereas the last two are caused by flooding or condensation corrosion. Many of the speleothems in fact experienced several episodes of dissolution followed by regrowth. The latest episode appears to be caused by condensation corrosion rather than flooding. Eleven speleothems containing growth hiatuses were dated by U-series methods. The results indicate that growth cessation did not occur synchronously. Furthermore, the timing of the hiatuses during the Quaternary is not restricted to glacial or interglacial periods. Oxygen and carbon stable isotope analyses of seven of the samples reveal an apparent shift towards a drier and warmer climate around 120 ka. However, more data and further collaborative evidence is desirable. Of six samples with hiatuses, five show a bi-modal distribution of stable isotope values: before and after the hiatus. Oxygen isotope analyses of modern drip water found inter-sample variations of over 2[per thousand]. This is due to cave environmental factors such as evaporation, infiltration velocity and roof thickness. Inside the caves δ 18 O of drip water decreases with increasing distance from the entrance and thus decreasing external climatic influence. This distance-climatic effect is also reflected in the δ18 O calculated for modern calcite: -5.3, -6.5 and -7.6[per thousand] VPDB at 3, 10 and 20 m respectively. The morphology of bell holes, found only in certain Notch caves, was studied in detail. It is proposed that the bell holes are formed by condensation corrosion, probably enhanced by microbiological activity. The study represents a comprehensive and thorough analyses of karst features on a small oceanic island, and provides information useful for climatic reconstruction during the Quaternary

The role of condensation in karst hydrogeology and speleogenesis, 2000, Dublyansky V. N. , Dublyansky Y. V.

Condensation in karst occurs over a wide range of natural settings, at latitudes from 25 to 70o and altitudes from sea level to 2600 m. In summer (April through September), condensation introduces a significant amount of water into the karst massifs (from 0.1 % to as much as 20 % of the total dry-season runoff). Contrary to common belief, in winter evaporation does not withdraw appreciable amounts of water from the massifs. Evaporating at depth, the water condenses near the surface within the epikarstic zone or on the snow cover and flows back. Condensation can sustain springs during prolonged dry periods (such as summer and winter) when there is no recharge by liquid precipitation. Condensation can play a significant role in speleogenesis, and many forms of cave macro-, meso-, and micromorphologies are attributable to condensation corrosion. It can be particularly efficient in the latter stages of hydrothermal cave development (during partial dewatering) when the temperature and the humidity gradients are highest. Coupled with evaporation, air convection, and aerosol mass transfer, condensation can play a crucial role in the formation of a number of speleothems, as well as create peculiar patterns of cave microclimate.

Hydrothermal speleogenesis in the Hungarian karst, 2000, Dublyansky Y. V.

Hydrothermal karst caves in Hungary were formed in a variety of speleogenetic settings. The oldest small solutional cavities (vugs) were formed in the deep-seated low-gradient zone at temperatures in excess of 90 oC. The temperatures decreased with time, as inferred from fluid inclusion studies of cave calcite. The caves were formed by normal carbonate corrosion. Large two-dimensional mazes of the Buda Hills were formed in the shallow low-temperature (but still hydrothermal) setting. The leading speleogenetic processes were normal carbonate corrosion (including mixing/cooling corrosion) and sulfuric acid corrosion. Temperatures at this stage were lower: ca. 50 oC and less. Above the thermal water table, in the subaerial zone, some specific and powerful speleogenetic processes occurred; condensation corrosion (by CO2-bearing waters) and replacement corrosion involving sulfuric acid reactions. Three-dimensional bush-like caves composed of connected spherical niches were formed as the result of this subaerial karstification.

Hypogenic caves in Provence (France). Specific features and sediments, 2002, Audra Philippe, Bigot Jeanyves, Mocochain Ludovic

Two dry caves from French Provence (Adaouste and Champignons caves) were until now considered as "normal" caves having evolved under meteoric water flow conditions. A new approach gives evidence of a hypogenic origin from deep water uprising under artesian conditions. Specific morphologies and sediments associated with this hydrology are discussed.

Hypogenic caves in Provence (France): Specific features and sediments, 2003, Audra Ph, Bigot J. Y, Mocochain L.

Two dry caves from French Provence (Adaouste and Champignons caves) were until now considered as “normal” caves, evolved under meteoric water flow conditions. A new approach gives evidence of a hypogenic origin from deep water uprising under artesian conditions. Specific morphologies and sediments associated with this hydrology are discussed.

Speleogenesis along sub-vertical joints: A model of plateau karst shaft development: A case study: the Dolný Vrch Plateau (Slovak Republic), 2003, Baroň, I.

Speleogenesis of narrow and relatively deep karst shafts (avens) was studied in the Slovak part of the Dolný Vrch Plateau (the Slovak Karst Biosphere Reserve, SE Slovakia). Most of the 211 shafts and shaft-related depressions located on the plateau have similar characteristics and no shaft has a known accessible connection to an active horizontal cave system. Dominant tectonic fractures are sub-vertical (sloping 70 - 90°) in most of the shafts. Several microforms, e.g. scallop-like forms, wall troughs or networks of protruding veins, evidence the main speleogenetic processes.
Water film dissolution extends the fractures, usually at the base of the epikarstic zone (Klimchouk, 1995), while the scallop-like forms develop. Then corrosive and erosive action of dripping water takes place and the wall troughs develop downwards - the shaft develops progressively now. Increased carbon dioxide concentration makes the solutions more aggressive and enables the processes working on the shaft bottoms. Water film action and selective condensation corrosion are responsible for upward shaft development. Later, shafts open to the surface, interacting with the effects of surface denudation.

On feasibility of condensation corrosion in caves (Comment to the paper: ''Hypogenic caves in Provence (France): Specific features and sediments'' by Ph. Audra, J.Y. Bigot and L. Mocochain), 2003, Dreybrodt, W.

In Fig. 6 of this paper the authors suggest how condensation corrosion could shape ceiling cupolas. Hot water containing high concentration of carbon dioxide rises to a lake filling the lower part of the cave room. Degassing of CO2 creates a CO2-containing atmosphere, which is heated by the warmer water below and becomes saturated with vapor, which condenses to the cooler wall of the cave, dissolves limestone and flows back to the lake.
If this process would continue in time it would be perfect to shape large cupolas. However, it does not because condensation stops when the temperature of the cave walls approaches that of the heated air. The reason is that condensation of water at the cave wall releases heat of condensation of 2.45 kJoule/g. This corresponds to an energy flux of 28 Watt/square-meter if a film of 1 mm depth would condensate to the wall in one day. In addition there is also a flux of heat from the warm air to the cave wall. Since the thermal conductivity of limestone (1.3 Watt/m°K) and its thermal diffusivity (5.6 x 10-7 m2/s) are low this heat cannot be rapidly transported into the bedrock, and consequently the temperature of the cave wall rises. Therefore the amount of condensation is reduced. 

One further comment should be given. There have been attempts to measure the effect of condensation corrosion by suspending gypsum plates freely in the air and determining weight loss after a defined time. For the reasons stated above the heat of condensation and the heat flux from the air raise the temperature of such samples much quicker than that of the cave walls. Reliable measurements can only be performed when such samples are fixed to the cave walls by using a high thermal conductivity glue.

A further suggestion to prove condensed water on cave walls is to take samples and analyse them for Ca-concentration and 13 carbon isotopic ratio. Since CO2 comes from the atmosphere exclusively should be below or close to zero, and Ca-concentration should be about 0.6 mmol/liter, when the pCO2 of the cave atmosphere is atmospheric.

Limestone wall retreat in a ceiling cupola controlled by hydrothermal degassing with wall condensation (Szunyogh model) (Comments to Wolfgang Dreybrodt remark ''On feasibility of condensation processes in caves'', Speleogenesis and Evolution of Karst Aqui, 2003, Lismonde, B.

Audra, Bigot and Mocochain (2003) proposed an explanation for the development of a hydrothermal cave in Provence ( France ), referring to the Szunyogh model (1989). Dreybrodt (2003) then shows by calculations that this model is unlikely. We will discuss Dreybrodt's answer here. Our conclusions will emphasise that Dreybrodt's hypothesis (transient conduction in a semi-infinite solid) is not the only possibility. When other conditions are considered (steady-state conduction with constant temperature at a finite distance), this cupola-development model can be valid.

The mechanism of wall retreat by corrosion linked to CO 2 degassing and water condensation is only possible providing the existence of a seepage flow close to the hydrothermal flow, which can maintain a sufficient thermal gradient over time.
The validity of Szunyogh's theory under these conditions has already been mentioned (Lismonde 2002, p. 292). Such a process also occurs in Movile cave ( Romania ), with values one order of magnitude lower as in our calculation. Condensation corrosion was demonstrated here using stable isotopes (Sarbu and Lascu 2001)

Rates of condensation corrosion in speleothems of semi-arid northeastern Brazil, 2004, Auler A. S. , Smart P. L.

Condensation corrosion is a little studied, but important dissolutional process that occurs within caves in many karst settings around the world (for a review see Dublyansky and Dublyansky, 2000). Condensation corrosion occurs when air equilibrates with the cave atmosphere, becomes acidic and dissolves the bedrock and speleothems. It is a later vadose process that apparently depends on air circulation patterns, number of entrances and general configuration (vertical range, presence of ponded water, passage shape, etc) of the cave. Both bedrock and speleothems can be affected by the process, resulting in weathered outer surfaces. Condensation corrosion in speleogenesis has been regarded as responsible for dissolutional modification during later stages of cave development of coastal (Tarhule-Lips and Ford, 1998) and hypogenic caves (Hill, 1987; Palmer and Palmer, 2000).
Condensation corrosion is a little studied, but important dissolutional process that occurs within caves in many karst settings around the world (for a review see Dublyansky and Dublyansky, 2000). Condensation corrosion occurs when air equilibrates with the cave atmosphere, becomes acidic and dissolves the bedrock and speleothems. It is a later vadose process that apparently depends on air circulation patterns, number of entrances and general configuration (vertical range, presence of ponded water, passage shape, etc) of the cave. Both bedrock and speleothems can be affected by the process, resulting in weathered outer surfaces. Condensation corrosion in speleogenesis has been regarded as responsible for dissolutional modification during later stages of cave development of coastal (Tarhule-Lips and Ford, 1998) and hypogenic caves (Hill, 1987; Palmer and Palmer, 2000).
The Campo Formoso Karst area of northeastern Brazil holds very extensive cave systems, such as Southern Hemisphere’s longest cave, the 97 km long Toca da Boa Vista. These caves show remarkable features of condensation corrosion such as cupolas, weathered cave walls yielding dolomitic sand, “air scallops” and corroded speleothems. Weathering rinds up to 5 cm thick occur in both dolomite bedrock and speleothem surfaces. Unlike the dolomite, speleothems usually do not disintegrate but change to a milky white opaque porous calcite that is in marked contrast with the fresh crystalline calcite. The area is presently under semi-arid climate and the cave atmosphere is characterised by high internal temperatures (2729 °C) and low relative humidity (mean of 73% for sites away from entrances).
Despite being such a widespread process, rates of condensation corrosion have so far been reported only from caves in the coastal area of the Caribbean (Tarhule-Lips and Ford, 1998). In this study, rates of condensation corrosion in speleothems were derived by determining thickness of weathering rind and age of last unaltered calcite. These rates represent minimum rates because speleothem growth ceased later than age obtained, and also condensation corrosion may not be continuous in time. Due to variable thickness of weathering layer (usually thicker at the top and thinner at sides of stalagmites), maximum and minimum thickness were obtained for each sample. Dating was performed through the alpha spectrometric U-series method in the first unaltered calcite layer beyond the weathering rim. 
The rates obtained vary over two orders of magnitude. They appear to be highly site specific, and are probably heavily dependent on the local atmospheric conditions, although more sampling is needed to confirm this relationship. The data shows that rates are dependent primarily on thickness measured, as range of ages is quite small. Tarhule-Lips and Ford (1998), in the very different littoral caves of the Caribbean, have estimated condensation corrosion rates based on experiments using gypsum tablets. Their reported mean value of 24 mm/ka, much higher than observed in the Campo Formoso caves, suggest that the process may be episodic in the area, not occurring during speleothem growth phases associated with wetter periods.
Although the rates reported by Tarhule-Lips and Ford (1998) indicate that condensation corrosion may actually enlarge cave passages in the normal (10 4 – 10 6 ka) time range of speleogenesis, in the Campo Formoso caves the process appears to play a minor speleogenetic role, being responsible for later modification of cave walls and speleothems.

Condensation Corrosion, 2004, James J. M.

Prediction of condensation in caves, 2005, Defreitas C. R. , Schmekal A.

Condensation is an important process in karst environments, especially in caves where carbon dioxide enriched air can lead to high rates of condensation corrosion. The problem is there has been very little research reported in the literature dealing with condensation as a microclimate process. This study addresses the problem and reports on a method for measuring and predicting condensation rates in a limestone cave. Electronic sensors for measuring condensation and evaporation of the condensate as part of a single continuous process of water vapour flux are tested and used to collect 12 months of data. The study site is the Glowworm tourist cave in New Zealand. Condensation is a function of the vapour gradient between rock surfaces in the cave and cave air. The size of the gradient is largely determined by air exchange with the outside. The results show that the numerical model to predict condensation works well. Given that rock-surface temperature in the cave does not vary much, condensation is essentially a function of cave air temperature and the processes that affect it, mainly, air exchange with outside. The results show that condensation can be controlled by controlling ventilation of the cave.

Condensation corrosion: a theoretical approach, 2005, Dreybrodt W. , Gabrovšek F. , Perne M.

Condensation of water from warm, humid air to cold rock walls in caves is regarded to play a significant role in speleogenesis.
The water condensing to the cave walls quickly attains equilibrium with the carbon dioxide in the surrounding air, and consequentlydissolves limestone or gypsum forming various types of macro- ,meso-, and micromorphologies. In this paper we present the basic physical principles of condensation and give equations, which allow a satisfactory estimation of condensation rates. Water condensing to a cooler wall releases heat of condensation, which raises the temperature of the wall thus reducing the temperature
difference ΔT between the warm air and the cave wall. Furthermore one has to take into account the heat flux from the air to the cave wall. This defines the boundary conditions for the equation of heat conduction. For a constant temperature of the air initial condensation rates are high but then drop down rapidly by orders of magnitude during the first few days. Finally constant condensation rates are attained, when the heat flux into the rock is fully transmitted to the surface of the karst plateau. For spherical and cylindrical conduits these can be obtained as a function of the depth Z below the surface. When diurnal or seasonal variations of
the air temperature are active as is the case close to cave entrances, condensation rates can become quite significant, up to about 10-6 m/year. The theoretical results are applied also to corrosion of speleothems and the formation of »röhrenkarren« as described by Simms (2003). To convert condensation rates into retreat of bedrock the saturation state of the solution must be known. In the appendix we present experiments, which prove that in any case the solution flowing off the rock is saturated with respect to limestone or gypsum, respectively