Brass, Copper, and Stainless Steel Pickling without using Nitric and Chromic Acids Italy 1992 Full scale

MANUFACTURE OF FABRICATED METAL PRODUCTS # 21

Background

Industrial brass and copper articles must be treated to eliminate superficial layers of oxide to give them a permanent smart appearance. In the traditional pickling technology, nitric and chromic acid are used with high atmospheric (NOx) and water (metal, nitrate, chromate) pollution hazards. In addition to waste streams treatment before release, gas and liquid disposal costs are also high. An alternative chemical pickling process, using organic peroxides was developed in 1992. It can be set up without plant modification, it is easy to operate and cost and quality effective. The technology is applicable to stainless steel coils, wire rods, tube, and in the treatment of stainless steel.

Cleaner Production Principle

Material substitution; Process modification; Recovery, Reuse and Recycle

Cleaner Production Application

This case study, illustrates a technology that makes use of organic peroxides for brass, copper and stainless steel pickling, lustering and surface passivation. Nitric and chromic acid are then eliminated with a consequent reduction of atmospheric emissions of NOx and elimination of NO3- and CrO4- ions in the waste water. Besides, simplifying the liquid waste purification, the technology makes the water processed reusable and therefore closes the loop. The electrolytic process can be applied to the recovery of metals contained in water out-streams. It has been in operation since 1987.

Environmental and Economic Benefits

The main cleaner production benefits are:

elimination of atmospheric pollution NOx from nitric acid reaction;
cleaner pickling reaction, hazardous material (100 tons/yr of nitric acid and 5 tons/yr are of chromic acid) are replaced by peroxides;
sludges reduced to 1/3;
closed loop recycling: purified output streams can be recycled to the pickling bath; and
resource conservation: less water, reagents, and energy consumption.

Regarding investment costs, the plant, though designed for the traditional technology, notes that it can manage the new process without modifications. Hence, further investment costs were not necessary for the implementation of the technology.

Considering the cost of the product, treatment, and of loss of metals, the traditional pickling using nitric and chromic acid ran about 100 lire/kilo and using the new technology costs ran 35 lire/kilo.

Constraints

None reported.

Contacts

ERGON s.r.l.
Via Battaglioni Edolo, 14
I 20034 Giussano
Milano Italy
Tel : +(39.3) 628.527.43
 
Mr C Fontant
Via Volta, 7
I - 20050 Verano Brianza
Milano, Italy
Tel : 39 362 907498; Fax : 39362 RE2743
 
Mr G Bardone
ENEA CRE Casaccia
Dip Ambiente
Via Anguillarese 301
00060 - S Maria di Galeria ROME
Italy
Tel : +(39.6) 3048 6662; Fax : +(39.6) 3048 3220

Review Status

This case study was submitted to UNEP IE in 1994 by Italy's ENEA. It was reviewed and edited by UNEP IE in July 1995.

Subsequently the case study has undergone a technical review by Dr Prasad Modak at Environmental Management Centre, Mumbai, India, in September 1998.