9th September 2010 17:01
|
Development of a New Procedure For The Recovery Of Zamak Pieces
|
|
  |
|
Problem Statement
Companies dedicated to metal finishing on zamak substrates frequently face problems related to obtaining coatings of good quality, giving rise to a high index of pieces which have to be rejected. |
Improvement Approach
Given the difficulty to develop an alternative electroplating procedure for zamak, the interest of our customer companies is centered in developing a demetallising method that could allow the recovery of the rejected pieces and their reuse in the process. |
Benefits
The project addresses two main benefits, coming from the recycling of the rejected pieces:
1. Economic savings
2. Lower environmental impact |
|
|
Company Contact Information
CIDETEC
Dr. Hans-Jurgen Grande; CIDETEC; Po. Mikeletegi 61-1; 20009 Donostia-San Sebastián; SPAIN
Tel.
+34 943 309022, Fax. +34 943 309136
E-mail
hgrande@cidetec.es
www.cidetec.es
|
|
|
|
|
|
One of the challenges which are frequently faced by the electrocoating companies is related to performing good quality electrolytic coatings on zamak and other zinc alloys. One can say that, at
the present time, there is no way to electrocoat great series of pieces of zamak with nickel, chrome, etc. if one does not
work within well-known and delimited conditions, as well as with electrolytes formulated specially for the process.
All this gives rise, of course, to a high amount of rejected pieces that, as well, implies a big problem as it is the recovery and recycling of the rejected pieces.
The origin of the problem is twofold: first of all, the composition and the structure of the substrate alloy, and second, the chemical and electrochemical composition and conditions of the electrocoating bath. |
In the case of zamak, trilayers of copper-nickel-chromium are deposited. The problem at the time of recovering a piece of zamak covered this way is not related to the demetallising of the chromium or nickel layers, but in the elimination of the copper layer.
The currently used processes for the recovery of zamak pieces are not satisfactory, since they lead to a surface attack on zamak, invalidating the recovery process. |
The target of the project has been the development of a new procedure for the recovery of electrolytically coated pieces of
zamak, with a triple metallic copper-nickel-chromium layer. The proposed procedure makes use of electrodissolution as a method for the selective elimination of the different metallic layers.
To carry out an electrochemical demetallising process, the substrate must be
inert, whereas the coating must be active. However, zamak is formed mainly by zinc, and this is one of the most active metals
than are used currently in the metal finishing industry.
For thatreason, although it is always possible to find a solution that attacks the coating metal, it is difficult to find solutions that do not affect the zamak substrate too.Therefore the main challenge in the project has been the development of a procedure that eliminates the coating without damaging the metal substrate. That has been accomplished by means of the use of suitable taylor-made corrosion inhibitors.
|
|
|
The new demetallisation procedure has been implemented in our customer company, giving rise to a 15% saving in the production costs. |
|
|
