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Problems do not stop when the fire is extinguished

Problems do not stop when the fire is extinguished Problems do not stop when the fire is extinguished Dr. Barry White, Principal Chemist of the Re-Tech Imbach Group The after effects of a fire can be a severe as thos e of the the moisture in air to give a vast range of metal oxides, fire itself. Th e cause of the deterioration whic h occurs in hydroxides and basic chlorides, re-forming the original buildings and equipment days after the fire has been acid in the process. extinguished is corrosion, and this corrosion can be Hydrochloric acid is volatile, so it can either stay prevented. where it is and cause further attack, or it can evaporate Th e most popular plastic material in the moder n world into the air and thus move onto another piece of metal is polyvinyl chloride (PVC). Britain alone used 445,000 causing it to corrode. tonnes of it in 1985. It is used for almost everything, fro m Even when the chloride had disappeared corrosion shoes to computer casings, milk crates to cable continues. Corrision is never uniform, it leads to insulation, telephones to flooring and doors and roughening of the surface and the development of pits, windows. Polyvinyl chloride is a polymer made by the pitting is self-propagating due to the phenomenon of joining of large numbers of molecules of vinyl chloride "different aeration". Oxyge n levels at th e botto m of these into a chain. Not only is PVC versatile, it is intrinsically pits are less than on the surrounding surface and as fire-retardant. It can burn, but only when strongly corrosion is more rapid at lower levels of oxygen , the pits heated. However, when it is heated t o above 200 degrees continue to get deeper even in the absence of the celsius it decomposes liberating hydrogen chloride chloride which initiated the process. (HCl) . A colourless chokin g gas, th e HCl combines with Chloride contamination of surfaces is universal. In our water to form hydrochloride acid. Some water is experience normal industrial or domestic surfaces provided by the combustion, some is taken from water which have not recently been cleaned, such as tops or vapour in the air and some is provided by the fire brigade doors or window-sills , wil l have abou t 3 t o 5 micrograms when extinguishing the fire. per square centimetres of chloride on them . A t this level The wate r pumped ont o the fire strongl y promotes the no problems wil l arise. However, at abou t 10 micrograms per square centimetre the risk of corrosion begins. corrosion process by helping to form hydrochloric acid, Anything above 20 micrograms will cause severe and assisting condensation on cooled surfaces, and main­ continuing corrosion. taining conditions of high humidity in the neighbourhood of the fire. Normal cleaning is not enough to get rid of the Hydrochloric acid is one of the most corrosive corrosion problem, it takes specialist knowledge to decontaminate an area thoroughly. It has taken us substances known. It attacks almost all metals. It is driven into crevices, machines, instruments and com­ several years t o develop techniques and cleaning fluids puters by the pressure produced by the fire. It penetrates to deal with all types of situations. concrete, converting carbonate t o chloride, and when it The corrosio n process is on-going , gettin g wors e wit h reaches any reinforcing in the concrete it attacks the time. It is therefore critical to address the problem by steel, forming iron chloride. This has a larger volume calling in experts as soo n as possible t o ensure that the than the massive iron, and thus the whole structure of damage which corrosion causes is arrested and the concret e can be broken by the expansion forc e of the minimised. corrosion process. All the normal metals used in equipmen t are attacked Details: RE-TECH IMBACH LTD, Linley Lodge Ind by the acid and all react to yield the chloride salts of the Est, Westgate, Aldridge, Walsall WS9 8EX. Tel 0922 metal concerned. These chloride salts react further with 54144. 12 ANTI-CORROSION October 1990 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Anti-Corrosion Methods and Materials Emerald Publishing

Problems do not stop when the fire is extinguished

White, Barry
Anti-Corrosion Methods and Materials , Volume 37 (10): 1 – Oct 1, 1990
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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0003-5599
DOI
10.1108/eb007283
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Abstract

Problems do not stop when the fire is extinguished Dr. Barry White, Principal Chemist of the Re-Tech Imbach Group The after effects of a fire can be a severe as thos e of the the moisture in air to give a vast range of metal oxides, fire itself. Th e cause of the deterioration whic h occurs in hydroxides and basic chlorides, re-forming the original buildings and equipment days after the fire has been acid in the process. extinguished is corrosion, and this corrosion can be Hydrochloric acid is volatile, so it can either stay prevented. where it is and cause further attack, or it can evaporate Th e most popular plastic material in the moder n world into the air and thus move onto another piece of metal is polyvinyl chloride (PVC). Britain alone used 445,000 causing it to corrode. tonnes of it in 1985. It is used for almost everything, fro m Even when the chloride had disappeared corrosion shoes to computer casings, milk crates to cable continues. Corrision is never uniform, it leads to insulation, telephones to flooring and doors and roughening of the surface and the development of pits, windows. Polyvinyl chloride is a polymer made by the pitting is self-propagating due to the phenomenon of joining of large numbers of molecules of vinyl chloride "different aeration". Oxyge n levels at th e botto m of these into a chain. Not only is PVC versatile, it is intrinsically pits are less than on the surrounding surface and as fire-retardant. It can burn, but only when strongly corrosion is more rapid at lower levels of oxygen , the pits heated. However, when it is heated t o above 200 degrees continue to get deeper even in the absence of the celsius it decomposes liberating hydrogen chloride chloride which initiated the process. (HCl) . A colourless chokin g gas, th e HCl combines with Chloride contamination of surfaces is universal. In our water to form hydrochloride acid. Some water is experience normal industrial or domestic surfaces provided by the combustion, some is taken from water which have not recently been cleaned, such as tops or vapour in the air and some is provided by the fire brigade doors or window-sills , wil l have abou t 3 t o 5 micrograms when extinguishing the fire. per square centimetres of chloride on them . A t this level The wate r pumped ont o the fire strongl y promotes the no problems wil l arise. However, at abou t 10 micrograms per square centimetre the risk of corrosion begins. corrosion process by helping to form hydrochloric acid, Anything above 20 micrograms will cause severe and assisting condensation on cooled surfaces, and main­ continuing corrosion. taining conditions of high humidity in the neighbourhood of the fire. Normal cleaning is not enough to get rid of the Hydrochloric acid is one of the most corrosive corrosion problem, it takes specialist knowledge to decontaminate an area thoroughly. It has taken us substances known. It attacks almost all metals. It is driven into crevices, machines, instruments and com­ several years t o develop techniques and cleaning fluids puters by the pressure produced by the fire. It penetrates to deal with all types of situations. concrete, converting carbonate t o chloride, and when it The corrosio n process is on-going , gettin g wors e wit h reaches any reinforcing in the concrete it attacks the time. It is therefore critical to address the problem by steel, forming iron chloride. This has a larger volume calling in experts as soo n as possible t o ensure that the than the massive iron, and thus the whole structure of damage which corrosion causes is arrested and the concret e can be broken by the expansion forc e of the minimised. corrosion process. All the normal metals used in equipmen t are attacked Details: RE-TECH IMBACH LTD, Linley Lodge Ind by the acid and all react to yield the chloride salts of the Est, Westgate, Aldridge, Walsall WS9 8EX. Tel 0922 metal concerned. These chloride salts react further with 54144. 12 ANTI-CORROSION October 1990

Journal

Anti-Corrosion Methods and Materials – Emerald Publishing

Published: Oct 1, 1990

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