Automotive components such as trims, door handles, head lamp surrounds, badges, hinges, switches, engine components and just about any complex shape you can think of on a car, was manufactured from an Aluminum Zinc based alloy called Mazak or Zamak.
This material could be molded under a process called high Pressure Aluminum Die Casting, which is a technique that involves injecting molten metal into a hardened tool steel mold and allowing it to solidify under pressure before ejection.
This resulted in a component with high accuracy, very good surface finish, and dimensional stability and strong enough for most automotive applications. The down side was that the material in certain environmental conditions could corrode. But to be fair motor manufacturers at that time never dreamed that 50 years on some of these vehicles would still be on the road.
Pitting occurs as the zinc in the material separates and precipitates out of the aluminum, sometimes as a process of electrolytic reaction. This process pushes up the surface and causes the plating to blister. Once we remove all the old layers of plating to reveal a pitted Aluminum casting. We cut the surface back to remove as much of the corroded surface as reasonably practicable. This also means that the original “cast skin” is removed in that process. So when we come to re-chrome we are not plating onto the same original surface. This means it’s harder to re-chrome than it was originally and can lead to the plating not adhering to the material. This is one of the reasons why most plating companies will not touch it!
Most you will read about Mazak repairs by other companies involves heavy copper plating to fill the pits. The truth is that copper does not fill the pits! But a successive layer with intermediate polishing spreads the copper over the pit to form an artificial skin. This skin can then be Nickel and Chromed to form a perfect result. The problem is a process called “crevice corrosion” may occur in the base of the pit and this is often accelerated by the presence of dissimilar materials in the plating process called “electrolytic corrosion”. I think we have all seen some at some time sheets of thick copper, plating peeling with rust beneath!
Our system won’t guarantee to give you a perfect result, but it will be longer lasting. Our process involves grinding and polishing to remove as much of the pitting as possible and then filling the larger pits. The following photos show a typical process of filling and polishing just one large pit. In practice some castings with a large spread of corrosion it not be possible to remove all the pitting? Please read our terms and conditions.
The Mazak Repair Process
In the base of each pit is a carbon deposit that needs to be removed before any attempt can be made to fill the pit!
The next stage is to fill the pit with a special solder and flux. This filler material melts a just a few degrees lower than the melting point of the Mazak casting. Therefore you only have a short window period in which you can use it, before you melt the whole casting! This requires a great deal of skill and expertise.