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How to give ZAMAC the color of rusty iron


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Hello to you all.


I'm an enthusiastic "model maker" and left school a very long time ago.


My knowledge of chemistry reached the zero point.


Not because I didn't like it, but just by not using it anymore.


At the moment I'm busy making a self propelled bucket dredger (scale 1:25)


Including two engines and steam boiler.


Of Course she will be radio controlled and therefore almost fully self controlled in the engine room.


Using different sensors and a PIC, all self designed.


After learning how to use a 3D drawing program, I managed to get a dredge bucket to be printed.


That resin-print-model is used to create a mold in heat resistant silicone.


In that mold I poured liquid ZAMAC (Alloy of zinc,aluminium,magnesium and copper) and created a wear resistant "riveted" model bucket.


The weight is about 70 grams, capacity 27 mL.


Major problem is that the buckets are shining like cutlery.



Using:


Kalium Polysulfide (K2S3) someone advised me


or


Ferro 3 chloride (FeCl3) anotherone advised me


Did not work.



post-116296-0-13287900-1457194680_thumb.jpg



On the left the test, right the untreated.


It looks like the outer scin is to "hard", the parts that I worked on with a file became gray.


In the barn I had some pickling paste for stainless steel, consisting HNO3 and HF.


Drowning the two zamac parts for 20 seconds was enough to "clean" everything.


After rinsing in clean water, I brushed the black ("dust") from the surface.


After that I put both parts in the Ferro3chloride and left it for 2 hours, nothing happened.


Then one part I put in the Kalium polysulfide for 10 minutes and after that again in the FeCL3 for another hour.



This is where I got lost (I did not write down what axactly I did and for how long).


The second part eventually became nicely brown (iron rust look).



post-116296-0-13243800-1457194695_thumb.jpg





Does Kalium polysulfide have any influence?


Is it necessary to add some piece of iron in the FeCL?


I did have a test with some steel glued on the zamac-bucket and for me it looked better/faster to color the zamac.


(the steel is part of the chain, connecting the buckets to eachother, so it has to be on the bucket anyway)



Can someone please explain what is the proper way to color the zamak in the way that it look like very old rusted iron?


In a way that I can reduce the time getting the result (the last part 5 hours, and I have to do 51 buckets) and more important: That I know what I'm doing and why.



Thanks in advance.


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