Number
142-EN
Section
General Section
Use
Sector
Electricity, steam, gas water supply and sewage treatment
Function
Aerating and dearating agents
Corrosion inhibitor
Deodorizer
Reducing agent
Process
Other hot work operations with metals
Product category
Metal surface treatment products
Waster treatment chemicals
Application
Heating systems
Abstract
Hydrazine is used to protect boilers form corrosion by reducing the concentration of dissolved oxygen in the water and by contributing to the passivation of the metal surface of the installation. Hydrazine is a hazardous substance and alternatives have been found that give acceptable results.
Substituted substances
Hydrazine
CAS No. 302-01-2 EC No. 206-114-9 Index No. 007-008-00-3
Chemical group
Hydrazine and hydrazinium salts
Classification: hazard statements
H226 Flammable liquid and vapour
H350 May cause cancer
H331 Toxic if inhaled
H311 Toxic in contact with skin
H301 Toxic if swallowed
H314 Causes severe skin burns and eye damage
H317 May cause an allergic skin reaction
H400 Very toxic to aquatic life
H410 Very toxic to aquatic life with long lasting effects
Other adverse effects
The substance is: 2B carcinogen (IARC) as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).
Alternative Substances
Diethylhydroxylamine
CAS No. 3710-84-7 EC No. 223-055-4 Index No.
Chemical group
Hydroxylamine derivatives
Ascorbic acid
CAS No. 50-81-7 EC No. 200-066-2 Index No.
Chemical group
Lactones
Carbonohydrazide
CAS No. 497-18-7 EC No. 207-837-2 Index No.
Chemical group
Hydrazine derivatives; urea derivatives
Sodium bisulphite
CAS No. 7631-90-5 EC No. 231-548-0 Index No. 016-064-00-8
Chemical group
Sodium compounds; sulfites
Classification: hazard statements
H302 Harmful if swallowed
Sodium sulphite
CAS No. 7757-83-7 EC No. 231-821-4 Index No.
Chemical group
Sodium compounds; sulfites
Potassium hydroxide
CAS No. 1310-58-3 EC No. 215-181-3 Index No. 019-002-00-8
Chemical group
Potassium compounds; hydroxides
Classification: hazard statements
H302 Harmful if swallowed
H314 Causes severe skin burns and eye damage
Sodium hydroxide
CAS No. 1310-73-2 EC No. 215-185-5 Index No. 011-002-00-6
Chemical group
Sodium compounds; hydroxides
Classification: hazard statements
H314 Causes severe skin burns and eye damage
Reliability of information
Internet information: data are from an internet document and only a basic and partial evaluation could be performed
Reason substitution
CMR
skin/respiratory sensitizing
Other type of alternative
Physical degasification of water.
Hazard Assessment
Substance to be substituted: Hydrazine is: a 2A carcinogen (IARC), 1A or 1B carcinogen (CLP Regulation), a sensitiser (H317, H334; CLP Regulation) as listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC). Alternative substance: Unlike hydrazine none of the alternatives is classified as carcinogen. Sodium bisulphite is registered by as harmful if swallowed. Potassium hydroxide causes severe skin burns and eye damage and is harmful if swallowed. Sodium hydroxide causes severe skin burns and eye damage.
Description of Substitution
The use of hydrazine in steam and heating systems is due to its efficacy in reducing the oxygen levels in waters (which favours oxidation and builds up rust) and in creating a passivation layer on the metal surface. Alternatives to hydrazine are already in use. Some of them are presented in a short document, available in French. The organic alternatives include diethylhydroxylamine (DEHA) or ascorbic acid that is also safe to use in the food industry steam system, but is more expensive. The use of carbohydrazide is not a good alternative because is a skin sensitiser and generates hydrazine and formaldehyde in the system. Inorganic alternatives like sodium sulphite or bisulphite as well as sodium or potassium hydroxides may be used instead of hydrazine, but they increase the mineral content of the water. Substitution of hydrazine may be also achieved by implementing other processes like the physical degasification of water. Other alternatives mentioned by the document are hydroxypropyl hydroxylamine (HPHA), or polyamine additives. Adding substances like polyamines creates a protective film for the metal surface limiting oxygen diffusion and therefore the corrosion. Information on the safe use of these alternatives and on HPHA is not easily available from independent sources. Users have to rely mostly on producer information.
Case/substitution evaluation
DEHA is already largely used as alternative to hydrazine. It has technical advantages and is suited to a variety of operational conditions and types of boilers. DEHA is not a carcinogen or sensitiser. HPHA (CAS 97173-34-7) is not registered in the C&L inventory nor is it classified by the CLP regulation annex VI; hazards may be identified according to MSDS. New products containing polyamines (and amines) have in general proprietary formulations that are not disclosed, so users have to rely on the information included by the producer in the MSDS. Physical processes for water degasification may not reach the desired concentration for dissolved oxygen and chemicals might still be needed to further lower its level. TRGS 608 (1991) names possible substitutes for hydrazine in water and steam systems. Most of these are also mentioned in the case study 142-EN from 2008. The case study is therefore state of the art.
State of implementation
In use
Date and place of implementation
France
Availability ofAlternative
Alternatives available on the market
Type of information supplier
Research
Further information
Type of publication and availability
Fact sheet, in French
Publication source: author, company, institute, year
The Fact sheet was developed by CNAMTS and INRS, France and published by INRS on its website in 2008.
Publication source
Type of publication and availability
http://www.inrs.fr/accueil/produits/mediatheque/doc/publications.html?refINRS=FAS%2016
Date, reviewed
December 11, 2020