Hey All,
Yellow zinc passivated mild steel seems to be quite a common chassis material - maybe not so much now (apparently it's not very green?).
Anyway.. does anyone have a recipe for doing it yourself?
I'm not looking for 'kits', or dips that have trade names that kide their true chemical ingredients - I want to know the real chemistry of the process, but I can't find any internet sites that describe it.
Yellow zinc passivated mild steel seems to be quite a common chassis material - maybe not so much now (apparently it's not very green?).
Anyway.. does anyone have a recipe for doing it yourself?
I'm not looking for 'kits', or dips that have trade names that kide their true chemical ingredients - I want to know the real chemistry of the process, but I can't find any internet sites that describe it.
yellow chromate
It's a chromate conversion coating produced on the zinc from an acidified hexavalent chrome solution, with certain activators added (acetate, formate, chloride,fluoride, nitrate, etc.)
These are all proprietary solns. and I'm not at liberty to divulge their formulations, but a soln. of sodium dichromate in weak nitric acid migt be a starting point for a zinc plated chasis.
Why do you want this? it's mostly used as an undercoat for painting nowadays.
John L.
It's a chromate conversion coating produced on the zinc from an acidified hexavalent chrome solution, with certain activators added (acetate, formate, chloride,fluoride, nitrate, etc.)
These are all proprietary solns. and I'm not at liberty to divulge their formulations, but a soln. of sodium dichromate in weak nitric acid migt be a starting point for a zinc plated chasis.
Why do you want this? it's mostly used as an undercoat for painting nowadays.
John L.
Maybe I've got the wrong process name. The finish I am thinking of doesn't take paint. It's a golden-yellow finish with pinkinsh purple areas - almost like an oil film on water. The colour patterns make it look like it was diiped - they sort of follow water run marks.
The reason I want it, is that I have some 'old' 19-inch rack cases made like this - I've cut them up to make new chassis, but I need to do something to the cut edges to prevent corrosion, and make them look nice - preferably something that matches the original.
The reason I want it, is that I have some 'old' 19-inch rack cases made like this - I've cut them up to make new chassis, but I need to do something to the cut edges to prevent corrosion, and make them look nice - preferably something that matches the original.
I believe the process you are looking at is cadmium plated steel. It can leave a yellow/iridecent finish like you describe.
I doubt if you can DIY. Its hard (near impossible) to find local shops that will do it these days, as the chemicals used are under tight EPA controls.
You might try inquiring at places that chrome plate motorcycle parts. Lots of times they also do cad plate as a sideline.
I doubt if you can DIY. Its hard (near impossible) to find local shops that will do it these days, as the chemicals used are under tight EPA controls.
You might try inquiring at places that chrome plate motorcycle parts. Lots of times they also do cad plate as a sideline.
/sreten.
done this for.. oh 4 decades now
Nope...
All of the finishes you see are conversion coatings of one form or another
Iron/steel can be chromated or phosphated, zinc, cadmium, copper, aluminum etc. can be chromated to varying degrees, and can indeed be an undercoat for subsequent painting.
The process provides additional corrosion protection over the bare metal, depending on the soln. composition, alloy, etc.
Much of the "older stuff" with the greenish yellow/pinkish finish is yellow chromate, usually formed over zinc or cadmium plating.
Not something a DIY-er will probably be successful at, although as I stated b4, you can try with acidified sodium dichromate / HNO3 solutions.
John L.
Nope...
All of the finishes you see are conversion coatings of one form or another
Iron/steel can be chromated or phosphated, zinc, cadmium, copper, aluminum etc. can be chromated to varying degrees, and can indeed be an undercoat for subsequent painting.
The process provides additional corrosion protection over the bare metal, depending on the soln. composition, alloy, etc.
Much of the "older stuff" with the greenish yellow/pinkish finish is yellow chromate, usually formed over zinc or cadmium plating.
Not something a DIY-er will probably be successful at, although as I stated b4, you can try with acidified sodium dichromate / HNO3 solutions.
John L.
Re: done this for.. oh 4 decades now
I believe John L is right with chromate, it's the kind of metallic yellow with a slight neon green hint coloured finish
http://en.wikipedia.org/wiki/Passivation
http://www.finishing.com/117/28.shtml <----- This is the place to ask about finishing, if you can do it someone here probably has done it...
http://www.caswellplating.com/ <----- sell various finishing kits for home scale work that can achieve professional results more than once and don't involve industrial equipment. Don't know if they have a chromate kit, but you can ask - they'll be much more geared towards your needs than any industrial supplier, and probably more helpful
From memory, I think phosphorus forms phosphoric acid at some percentage when dissolved in water. Phosphorus is a primary ingredient in meth synthesis, so if you're going to buy it expect questions and possibly visits. Although, if you have a genuine use, you have nothing to worry about in that respect. It is also available from strike anywhere matches of coarse. Phosphorus, and most things containing it, are toxic (not just harmful).
John
auplater said:
I believe John L is right with chromate, it's the kind of metallic yellow with a slight neon green hint coloured finish
An externally hosted image should be here but it was not working when we last tested it.
http://en.wikipedia.org/wiki/Passivation
http://www.finishing.com/117/28.shtml <----- This is the place to ask about finishing, if you can do it someone here probably has done it...
http://www.caswellplating.com/ <----- sell various finishing kits for home scale work that can achieve professional results more than once and don't involve industrial equipment. Don't know if they have a chromate kit, but you can ask - they'll be much more geared towards your needs than any industrial supplier, and probably more helpful
From memory, I think phosphorus forms phosphoric acid at some percentage when dissolved in water. Phosphorus is a primary ingredient in meth synthesis, so if you're going to buy it expect questions and possibly visits. Although, if you have a genuine use, you have nothing to worry about in that respect. It is also available from strike anywhere matches of coarse. Phosphorus, and most things containing it, are toxic (not just harmful).
John
It's always been my understanding that the iridescent coating used on steel was an aluminum coating. See here:
http://www.finishing.com/121/17.shtml
Not something uou could do yourself, it would appear (although look at some of the exotic things people do on this forum).
If it's just the cut edge as you suggest, I would simply grind/file/sand/buff smooth and then hit it with a sealant such as lacquer or clear nail polish to prevent corrosion. The alternative is to clean up the edge and take the whole piece for nickel or chrome plating.
Also, be aware that some of the things discussed here, like cadmium and hexavalent chromium are quite toxic and constitute a health hazard and may create hazardous waste that shouldn't be dumped down the drain.
--Bukapound
http://www.finishing.com/121/17.shtml
Not something uou could do yourself, it would appear (although look at some of the exotic things people do on this forum).
If it's just the cut edge as you suggest, I would simply grind/file/sand/buff smooth and then hit it with a sealant such as lacquer or clear nail polish to prevent corrosion. The alternative is to clean up the edge and take the whole piece for nickel or chrome plating.
Also, be aware that some of the things discussed here, like cadmium and hexavalent chromium are quite toxic and constitute a health hazard and may create hazardous waste that shouldn't be dumped down the drain.
--Bukapound
Buckapound said:
^This is true, and not in the sense that bleach is hazardous, you really need to take care with metal finishes.
Not sure about an aluminium coating. Zinc is the coating used on most steel. You can get things galvanised if you just find the local galvinisers and get friendly. They usually do industrial sized batches of railings and other stuff like that, but could probably be talked into doing a chassis. They just hook them onto a conveyor and it goes through a huge zinc bath that's continually kept molten - usually 24/7. You need to make sure you can't end up with pockets of trapped air if you galvanise anything, that's why fence and gate posts have holes drilled in them somewhere - to let the air pocket inside the single ended tube escape as it goes into the bath, allowing the inside to be coated.
Personally, it'd be cheaper and easier to just take it to anywhere that might be equipped with a spray booth or powder coat oven and get it painted. There are even guides for a cheapo DIY powder coating gun and videos of the results on YouTube - it uses a tiny, $5-10, over the net, high voltage generator for air ionisers I think, the diode multipler kind. You can cook the powder in a kitchen oven (raid one from the dump).
Those yellow bits in the photo look like what I have, though mine is more 'yellow'. If anyone has ReVox machines, they are done like that inside.
Phosphoric acid is very easy to get here - just about every hardware store sells it. It works very well funtionally, but it doesn't give a 'pretty' result.
I do have already a bottle of potassium dichromate, so I'll give that a try - thanks for the suggestions all.
Since I only want (at the moment) a very little done, it doesn't make sense to get someone to do it for me, or to buy a kit that produces many litres.
Phosphoric acid is very easy to get here - just about every hardware store sells it. It works very well funtionally, but it doesn't give a 'pretty' result.
I do have already a bottle of potassium dichromate, so I'll give that a try - thanks for the suggestions all.
Since I only want (at the moment) a very little done, it doesn't make sense to get someone to do it for me, or to buy a kit that produces many litres.
Zinc electroplating
yes... but I'd hardly call it "poor man's galvanizing"...
It's been passivated/enhanced with a chromate conversion coating.
If my word isn't good enough, here's a "cite"... :-;
http://en.wikipedia.org/wiki/Chromate_conversion_coating
John L.
yes... but I'd hardly call it "poor man's galvanizing"...
It's been passivated/enhanced with a chromate conversion coating.
If my word isn't good enough, here's a "cite"... :-;
http://en.wikipedia.org/wiki/Chromate_conversion_coating
John L.
I was just reading up the wiki stuff on the dangers of hexavalent chromium... and remembering that at school (middle-, high school, not university) we were given free access to all these chemicals, & encouraged to do all kinds of simple experiments with them to learn their properties (i.e, heat them, dissolve them in various solvents, do flame tests), though tasting them was specifically banned!
hex chrome
You haven't lived until you've experienced a hydrogen gas explosion of the foam mist suppression blanket on a 170 F 500 gallon chromic acid chrome plating tank, when a neophyte doesn't make firm contact with the cathode bus carrying hundreds of amps at 12+ volts and draws a spark!!
John L.
Steerpike said:
You haven't lived until you've experienced a hydrogen gas explosion of the foam mist suppression blanket on a 170 F 500 gallon chromic acid chrome plating tank, when a neophyte doesn't make firm contact with the cathode bus carrying hundreds of amps at 12+ volts and draws a spark!!
John L.
Yellow zince ...
Hi
This is OT as Steerpike enquired about surface coating of steel.
I recently needed to anodise 'simulated gold' on aluminium. These tints are expensive and here is the result I got by using yellow food colouring @ about US$1 per bottle. I used about 1 desertspoonof the stuff on 1 litre of deionised H2O. The result looks better in real life - nice and metallic like.
bulgin
Hi
This is OT as Steerpike enquired about surface coating of steel.
I recently needed to anodise 'simulated gold' on aluminium. These tints are expensive and here is the result I got by using yellow food colouring @ about US$1 per bottle. I used about 1 desertspoonof the stuff on 1 litre of deionised H2O. The result looks better in real life - nice and metallic like.
bulgin
Attachments
You know...
Zinc platings have a convinient side benefit. Zinc is "sacrifical"... it will corrode in preferece to bare steel it is electrically connected to. This means that your cut edges may not corrode as rapidly or severely as you may think. The zinc right along the ocrners of the cut will protect the rawsteel.
The is one reason why galvanizing is so popular. The typical pipe wrench mangles the coating on the pipe... yet the pipe remains protected.
I use preplated (zinc) steel in chassis structures all the time... saves the cost of plating individual pieces... and provides reasonable protection.
I would just put some clear fingernail polish down the edges before I bought all the nasty chemicals. And keep in mind that if you wish to plate these areas... all prior plating must be removed...
Zinc platings have a convinient side benefit. Zinc is "sacrifical"... it will corrode in preferece to bare steel it is electrically connected to. This means that your cut edges may not corrode as rapidly or severely as you may think. The zinc right along the ocrners of the cut will protect the rawsteel.
The is one reason why galvanizing is so popular. The typical pipe wrench mangles the coating on the pipe... yet the pipe remains protected.
I use preplated (zinc) steel in chassis structures all the time... saves the cost of plating individual pieces... and provides reasonable protection.
I would just put some clear fingernail polish down the edges before I bought all the nasty chemicals. And keep in mind that if you wish to plate these areas... all prior plating must be removed...
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