Number
066-EN
Section
General Section
Use
Sector
General manufacturing, e.g. machinery, equipment, vehicles, other transport equipment
Manufacture of fabricated metal products, except machinery and equipment
Manufacture of basic metals, including alloys
Function
Cleaning agent
Process
Treatment of articles by dipping and pouring
Product category
Metal surface treatment products
Application
Cleaning metal parts before coating
Abstract
Metallic coating on metal parts is often performed by galvanic processes. To achieve good-looking surfaces of good quality it is necessary to first clean the items. Earlier the company used sulphuric acid for pickling. The acid was heated and therefore some of it evaporated from the tank. By substituting sulphuric acid with hydrochloric acid pickling not only became more efficient, moreover, hydrochloric acid does not need to be heated.
Substituted substances
Sulphuric acid
CAS No. 7664-93-9 EC No. 231-639-5 Index No. 016-020-00-8
Chemical group
Inorganic acid
Classification: hazard statements
H314 Causes severe skin burns and eye damage
Other adverse effects
Strong inorganic acid mists: 1 carcinogen (IARC) as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).
Alternative Substances
Hydrogen chloride
CAS No. 7647-01-0 EC No. 231-595-7 Index No. 017-002-00-2
Chemical group
Inorganic acid
Classification: hazard statements
H331 Toxic if inhaled
H314 Causes severe skin burns and eye damage
Other adverse effects
Strong inorganic acid mists: 1 carcinogen (IARC) as listed in the Substance Database according to SUBSPORT Screening Criteria (SDSC).
Reliability of information
Evidence of implementation: there is evidence that the solution was implemented and in use at time of publication
Reason substitution
other toxic effects
Hazard Assessment
Substance to be substituted: Sulphuric acid (as strong orcanic mists) is carcinogenic to humans (Group 1), according to the IARC Monographs. It fulfils the criteria to be listed in the Substance Database according to SUBSPORTplus Screening Criteria (SDSC). Alternative substance: Hydrogen chloride is not listed in the SUBSPORTplus Database. » Check the Substance Database according to SUBSPORTplus Screening Criteria (SDSC)
Description of Substitution
Metal parts are coated by galvanic processes. To achieve good-looking surfaces of good quality it is necessary to first clean the items. An alkaline treatment removes oil and debris and an acid treatment (pickling) removes rust and filament shells. In practice, metal parts are dipped in a specific order into process baths of various chemicals for an appropriate period. After each treatment the items have to be rinsed with water in one or more cleaning baths and then are migrated to the next bath and so forth. The company had used sulphuric acid for degreasing, which was heated and therefore some of the acid evaporated from the tank. By substituting sulphuric acid with hydrochloric acid pickling not only became more efficient, moreover, hydrochloric acid does not need to be heated at all. The substitution took place in the summer of 2011. Despite the harsh classification of both acids, employees did not report difficulties regarding to their working environment. The substitution did change that. Degreasing with hydrochloric acid takes as long as degreasing with sulphuric acid. Since hydrochloric acid does not need to be heated less vapour is formed as compared to the treatment with sulphuric acid. Moreover, less electricity is used because the degreasing acid does not need to be heated. Hydrochloric acid cleans the items even a little bit better than sulphuric acid. Therefore, the overall quality of the galvanic process has improved. Procurement costs and consumption of the two acids are the same. Less of the acid evaporates and therefore the environmental impact is controlled better. Since more acid waste is generated (because of lesser evaporation) expense for handling the hazardous waste has increased.
Case/substitution evaluation
Both acids are not in themselves defined as hazards in the hazardous Substance Database according to SUBSPORT Screening Criteria (SDSC). The mists of strong inorganic acids are however carcinogenic according to IARC. Therefore, both acids would not pass the criteria. The alternative is also more hazardous than the substituted substance. On the other hand, the new method where the acid does not need to be heated reduces acid evaporation. This is proven by the increased amount of hazardous waste. The hazardous waste can be disposed in a better controlled and therefore safer way as compared to the vapour. The reduced diffuse spread to the environment is an advantage for employees as well. The employees do, however, handle a more hazardous acid compared to the situation before. This hazard is managed by a controlled workflow which warrants the employees’ safety. Therefore, the substitution measures should be improved. In the BVT Information Sheet “Electroplating” this substitution is described. Therefore it is currently state of the art.
State of implementation
Full capacity
Date and place of implementation
Summer 2011 in Denmark
Availability ofAlternative
Easily available
Type of information supplier
User
Contact
Date, reviewed
December 11, 2020