8th September 2010 0:58

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	Technology Watch Knowledge Base

Replacement of Steel with Scratched Zamak

Problem Statement
The customers main objective was to implement industrially a new scratching process on zamak, giving a finish similar to stainless steel but with smaller production costs.

Improvement Approach
The main development in the new process involved the direct scratching of the surface of the piece of zamak, prior to the deposition of an improved protection coating, thus obtaining a product whose aspect and properties were similar to those of steel.

Benefits
By implementing the new process on an industrial scale the customer has increased its quality levels and competitiveness. Among other benefits, the number of stages for the complete scratching process has been reduced from 27 to only 8.

Company Contact Information
Fundación TEKNIKER
CIDETEC - Dr. Hans-Jurgen Grande- Po. Miramon 196; 20009 Donostia-San Sebastián; SPAIN
Tel. +34 943 309022, Fax. +34 943 309136
E-mail hgrande@cidetec.es
www.cidetec.es

PROBLEM STATEMENT

The customer company uses mainly zamak (especial zinc alloy) as a base material for the manufacture of decorative articles. Pieces made from this material can be easily obtained by extrusion and they can be further submitted to metal electrocoating processes, giving rise to an improvement in their surface properties and appearance.
However the customer company faced a problem, also affecting all the other companies of decorative metallic components market. New architectonic designs have standardised the use of stainless steel decorative elements as a way to guarantee the surface protection of the structural parts of buildings. Nevertheless, stainless steel is excessively expensive for the market. For that reason, the user company developed in 1997 a new process for introducing in the market an imitation of stainless steel having the good characteristics of corrosion resistance. This process includes the electrodeposition of copper and later nickel on a piece of zamak.

Next the nickel-plated surface has to be submitted to a manual scratching process, and afterwards a transparent lacquer layer is applied in order to protect the surface and improve its finish.
This procedure provides quite satisfactory results in terms of the finish of the final product. However, the process is extremely problematic, due to the hardness of nickel coatings, giving rise to a product with elevated production costs, which are a consequence of the excessive manual labor entailed.
Therefore the customer company considered it a priority to develop a new improved industrial implementation of the scratching process on zamak, giving a similar finish to stainless steel with smaller production costs.

IMPROVEMENT APPROACH

The test case has addressed the technology area of metal manipulation and finishing, and its application to the manufacture of domestic decorative appliances. The main idea in introducing the new process involved the direct scratching of the surface of the piece of zamak, prior to the deposition of an improved protection coating, thus obtaining a product whose aspect and properties are similar to those of stainless steel. There has not been a similar or identical solution before. Other companies have absorbed the costs of using stainless steel in their decorative pieces and components.
The methodology has included the accomplishment of 3 tasks during 3 months, including both experiments at laboratory and pilot-plant scale and tests at industrial scale for the adequate implementation of the process.
During the first stage of the test case, a feasibility study of the direct zamak scratching process was performed. The effect of the different variables that controlled the process i.e. type of abrasives and tools to be use used, among others, were analyzed.

The second stage was centered on the development of a surface conditioning procedure.
As a result of the scratching process the pieces become dirty and unactivated, thus interfering in the quality of the finishing. Hence a new process for the cleaning and activation of the surface of the pieces was necessary. This involved the study of the effect of the chemicals to be used both in the cleaning process (alkaline, wetting or tensoactive agents) and in the activation process (activating acids, corrosion inhibiting agents). The work conditions, such as pH, treatment time, temperature of the process, etc, were analyzed and optimised.
The final task was focused on implementing a suitable formulation for a protective layer to be electrophoretically deposited on the scratched zamak surface, taking as a close reference the protective formulations used for current scratching processes. This formulation includes resins, organic solvents and coloring agents, which neither generate porosity in the resulting coating nor produce any other damage in the properties of the decorative shape.

BENEFITS

By implementing the new zamak scratching procedure the customer company has clearly increased its quality levels and competitiveness. Among other benefits, the number of stages of the complete scratching process has been reduced from 27 to only 8.
The process presents in addition other advantages:
(1) the pieces are introduced only once in the electroplating line,
(2) there is a remarkable decrease in manual labour,
(3) non-use of metallic coverings, thus implying non-use of heavy metals (nickel, chromium),
(4) non-use of chromic passivation,
(5) easy purification of effluents, since there are no cyanide containing waters, neither chromic waters,
(6) smaller percentage of pieces rejection,
(7) and lower final cost of the pieces.

The customer company expects to reach annual savings of about 20.000 €, and the pay-back time of the implemented process is estimated in around 18 months. In addition, the customer has gained experience and a better knowledge of their current production processes.


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