Number
283-EN
Section
General Section
Use
Sector
Manufacture of fabricated metal products, except machinery and equipment
General manufacturing, e.g. machinery, equipment, vehicles, other transport equipment
Function
Cleaning agent
Process
Manual activities involving hand contact
Product category
washing ad cleaning products
Application
Substituting hydrofluoric acid
Abstract
One of Denmark’s largest manufactures of gold jewellery has successfully substituted hydrofluoric acid with sulphuric acid. The acid treatment is necessary for removing the plaster of the casting mould. Compared to hydrofluoric acid, sulphuric acid is not always capable of dissolving all plaster residues, so in some cases manual treatment has to be applied. Hydrofluoric acid is highly hazardous to work with compared to sulphuric acid.
Substituted substances
Hydrofluoric acid
CAS No. 7664-39-3 EC No. 231-634-8 Index No. 009-003-00-1
Chemical group
Fluorine compounds; inorganic acids
Classification: hazard statements
H310 Fatal in contact with skin
H330 Fatal if inhaled
H300 Fatal if swallowed
H314 Causes severe skin burns and eye damage
Alternative 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).
Reliability of information
Evidence of implementation: there is evidence that the solution was implemented and in use at time of publication
Evidence of assessment: there is evidence of an official (positive) assessment of the substitution
Reason substitution
skin/respiratory sensitizing
Other type of alternative
In addition to acid treatment, scraping and polishing is used to remove plaster residues.
Hazard Assessment
Substance to be substituted: Hydrofluoric acid is fatal if swallowed, if inhaled and in contact with skin and it causes severe skin burns and eye damage. Alternative substance: Sulphuric acid is not listed in the SUBSPORTplus Database. Sulphuric acid as mist/aerosol is included in SDSC, but this case only involves soaking in closed vessels.
Description of Substitution
One of the post-casting steps in gold jewellery manufacturing is soaking in strong mineral acid to remove casting mould residues before further processing. Traditionally concentrated hydrofluoric acid is used. An acid that is famous for being extremely hazardous to work with, due to its lethally toxic properties. When a new acid treatment equipment arrived at the production site and showed not to meet the specifications, the heating units were made of glass, which corrodes in contact with hydrofluoric acid. The production manager, being very keen on occupational safety, decided that the time was up to try something new; to get rid of hydrofluoric acid for the sake of the employees and the environment. A number of strong mineral acids were tested for their ability to dissolve the burned plaster from the gold alloy, and sulphuric acid proved to be the best candidate. Now it is the only acid used in the cleaning process. All acid treatment is done in a separate ventilated room in closed vessels, and all acid is collected for retrieval of dissolved precious metals and further safe disposal. The casters and goldsmiths have embraced the new procedure although it sometime means that they have to apply some manual work in removing the last plaster residues from the gold items. As far as informed; this is the only larger gold jewellery production site in EU that has substituted hydrofluoric acid in the cast removing process.
Case/substitution evaluation
This case is a good example on that less hazardous and less polluting alternatives are available for an industry that tend to very traditional in its approaches to changes in the production process. The production manager hopes that this case will serve as an inspiration for other gold jewellery manufacturers.
State of implementation
In use
Date and place of implementation
2010 Denmark
Enterprise using the alternative
Availability ofAlternative
On the market
Producer/Provider
Sulphuric acid in various concentrations and grades are avaliable from a number of industrial chemical suppliers.
Type of information supplier
User
Contact
Date, reviewed
November 26, 2021