ruffrecords

Steel for enclosures
« on: March 14, 2019, 11:22:26 AM »
When I started the Mark 3 tube mixer design one of the objectives was to replace the expensive extruded aluminium module enclosures with a simpler cheaper design. To cut a long story short the final design uses a single steel sheet because it screens both electrically and magnetically (which the aluminium ones did not). A while back I got some cold rolled mild steel cut to size and used it for building mock ups and prototypes. Some months later I notice the steel is starting to rust. So now I am on the hunt for the kind of steel typically used in Neve modules - you know the sort with the kind of buttery golden finish. I have not idea what this is called but I have been surfing extensively. I have come across a materiel called Zintec (also known as electro zinc)which is mild steel with a thin electrolytically applied coating of zinc. According to one web site:

"Zintec is the trade name for a form of treated mild steel that has been treated with a thin layer of zinc, which protects the steel against corrosion and rust. Cold reduced, mild steel sheet is first electrolytically cleaned and then pickled to give it a clean, smooth oxide free surface before it’s coated with a uniform, electrolytic deposit of zinc or a zinc-nickel alloy. We use Zintec sheet metal for metal work that doesn’t need a full zinc plate treatment but would rust if only made from mild steel.  Many internal components are ideally suited to zintec steel such as electronics chassis, lighting gear trays, brackets, sheet metal enclosures and cabinets and any sheet metal fabrications that won’t be getting wet and are not cosmetically important."

So it looks like it will do the job, it is relatively inexpensive but apparently it is a dull grey in colour so it is not the stuff Neve used. There seems to be further passivation processes you can apply to zinc coated steel to further improve corrosion resistance, some of which also alters the appearance. But I am not closer to finding the correct name for the material or process I need. Any idea?

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'


JohnRoberts

Re: Steel for enclosures
« Reply #1 on: March 14, 2019, 02:14:43 PM »
Paint? Powder coat? 

We used to buy a vinyl coated steel that we could bend without breaking the vinyl.

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Ilya

Re: Steel for enclosures
« Reply #2 on: March 14, 2019, 02:30:03 PM »
Isn't that yellowish color just a passivated mild steel? I think there are chemical solutions that allow you to passivate a steel at home. Haven't tried this though.
PCBs, enclosures and build guides at www.rackneve.com

ruffrecords

Re: Steel for enclosures
« Reply #3 on: March 14, 2019, 02:51:34 PM »
Isn't that yellowish color just a passivated mild steel? I think there are chemical solutions that allow you to passivate a steel at home. Haven't tried this though.

As far as I can make out, you cannot passivate steel, You can plate it (with something like zinc) and then passivate the coating. Apparently the proper meaning of passivate is to grow an oxide coating - in steel that is rust which is what we are trying to stop.

On the other hand something like that might well be called passivated steel. It is all very confusing.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

ruffrecords

Re: Steel for enclosures
« Reply #4 on: March 14, 2019, 02:59:52 PM »
I think I found the (techical) answer. Quote from another web site:

"Zinc plating involves zinc metal being electrodeposited on to components. Zinc plating is passivated to give it corrosion resistance and the zinc plating protects the underlying material further by being sacrificial. Zinc electroplating is a form of electrochemical galvanization. The passivation on zinc plating determines its final colour - we can offer clear (blue tinted, trivalent), colour (yellow iridescent, hexavalent) or black (black, trivalent). Thicknesses of 5µm, 8µm, 12µm and 25µm are common, but other thickness are available on request. We offer bright zinc plating on components made of steel, stainless steel, copper, brass and bronze.

I have highlighted the key section in red. Looks like I need hexavalent zinc passivated steel. Back to Google.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

JohnRoberts

Re: Steel for enclosures
« Reply #5 on: March 14, 2019, 03:00:31 PM »
zinc chromate?

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

ruffrecords

Re: Steel for enclosures
« Reply #6 on: March 14, 2019, 03:05:29 PM »
zinc chromate?

JR

Er, yes but it turns out that the use of hexavalent chromium is now banned by the EU under the ROHS directive.

But, some companies are offering the same colour finish using trivalent chromium which is OK ( I think).

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

shabtek

Re: Steel for enclosures
« Reply #7 on: March 14, 2019, 03:24:53 PM »
These processes would need to be performed after the  sheet stock has been cut/drilled and bent to final dimensions to avoid raw edges—I’d assume

I’ve made chassis’ from ‘galvanneal’ sheetstock. The name indicates some kind of zinc additive. It is ferromagnetic. I’ll have to look closer but don’t recall corrosion on the raw edges even after a few years in my damp shed. It is not as nice as what Rupert used.

"really fine players do not use stomp boxes or master volume, they match the amp to the room and turn it up to 11.  Stevie Ray, BB King, Albert King, Duane Allman, Dicky Betts, Louis Armstrong"
   -CJ

JohnRoberts

Re: Steel for enclosures
« Reply #8 on: March 14, 2019, 04:58:27 PM »
I recognize the name galvaneal from way back in the cobwebs of my metalworking memory.

JR
Visit https://circularscience.com to hear what properly "cleared" drums sound like.

Re: Steel for enclosures
« Reply #9 on: March 14, 2019, 05:47:07 PM »
Im not sure what the plating on Marshall amps is ,the older ones have either zinc or galvanised with a laquer coat , it gives it a slightly golden appearance ,

I think there was one Russian guy who did a run of Neve stuff and he managed to get a similar plated finish to the originals , not chrome ,but more yellow shiney ,Nickel id imagine .

The laquer attracts a layer of dust over the years ,doesnt really clean up too well and if you scrub it overenthusiastically your back to bare metal , if its kept clean and its in an inacessable place it does last a lifetime though .


Walrus

Re: Steel for enclosures
« Reply #10 on: March 14, 2019, 08:04:00 PM »
When I worked for International Rectifier amny years ago, we refered ti the yellow plating as Tropicalizing. Can't remember if we did it in house, but we certainly had a tin plating bath for the big diodes/thyristors.
Kevin.

pvision

Re: Steel for enclosures
« Reply #11 on: March 14, 2019, 08:20:59 PM »
The advantage of zinc plating is that it creeps over scratches & marks to "heal" itself and prevent rusting

I have passivated steel bolts on my BMW 2002 which, when removed, look perfect some 44 years after the car was built

Nick Froome

Brian Roth

Re: Steel for enclosures
« Reply #12 on: March 14, 2019, 10:57:57 PM »
Ian, I recall something very similar on steel sheet metal parts used on Ampex recorders eons ago.  In many cases, it often had some colored "swirls" mixed in with the yellow color.  I recall it being called Zinc Chromate.

I posted a question on the Ampex mailing list, which has many old-timers from that era, and will forward their comments.

Back in the 1970's, I had some steel parts plated  by a local shop which resulted in that same finished look.

Bri

Brian Roth Technical Services
Salina Kansas, home of the best vinyl on the planet!

http://www.BrianRoth.com
recordingservicesandsupply.com/
www.qualityrecordpressings.com/
store.acousticsounds.com

[silent:arts]

Re: Steel for enclosures
« Reply #13 on: March 15, 2019, 03:38:56 AM »
Er, yes but it turns out that the use of hexavalent chromium is now banned by the EU under the ROHS directive.
Yes, yellow chromated is not allowed in the EU.
My 51x Racks are blue chromated, looks better anyway (but not blue).

ruffrecords

Re: Steel for enclosures
« Reply #14 on: March 15, 2019, 03:55:34 AM »
Yes, yellow chromated is not allowed in the EU.
My 51x Racks are blue chromated, looks better anyway (but not blue).

I am not too worried about the actual colour because they will be under the hood but it would be nice if they looked like the old Neve ones I rememeber just from a nostalgic point of view.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Brian Roth

Re: Steel for enclosures
« Reply #15 on: March 15, 2019, 07:26:36 PM »
Ian, I posted this to the Ampex mailing list:

In another forum that I frequent, one of the members is racking his brain trying to recall the processes that were used when he worked at Neve decades ago.  Ian currently builds custom tube mixers in the UK and is having some new steel parts fabricated which require surface protection.

What he described reminded what I recall seeing on steel sheet metal on Ampexii from that same era (cover plates on 440's and elsewhere).

Ian described it as a "buttery yellow".  I recall it having other colored swirls mixed in with the overall yellow:  maybe red and blue...maybe some green (RGB!  lol).

I had a local metal finishing shop plate some steel parts for me back in the 1970's which had that same look.  I THINK they called it zinc chromate, but Wiki investigations have left me confused.

Ideas?  Thanks!

Bri

And some useful info came back.

Reply #1:

There are cadmium and zinc finishes that both look yellow like that.
Zinc chromate Type 2 and Cadmium Plate QQ-P-416 are the two that I
see on aviation parts.
--scott


Reply #2:

Yellow zinc is a common protection for steel parts.

Cadmium is now so toxic that very few will touch it, at least in the People's Republic of U and S.

My experience is that the yellow zinc process replaced the common 1950's cadmium plate process.

Bill


Reply #3:

I always heard it called cad plate by my late friend Brian Dall’Armi. He also affectionately called it “japananium”. That was indeed decades ago.
.Jerry


Reply #4:

The common yellow plating on many Ampex parts is yellow cadmium plate, also common on aircraft nuts and bolts. Pretty much impossible to get in the US now due to toxity of cadmium. Same is true of the chromic acid conversion on aluminum, different toxic chemicals. Passivated gold zinc plating is probably the best bet today. There are shops that will do this, typically for $200-600 minimum lot charge.


Hope that helps!

Bri

Brian Roth Technical Services
Salina Kansas, home of the best vinyl on the planet!

http://www.BrianRoth.com
recordingservicesandsupply.com/
www.qualityrecordpressings.com/
store.acousticsounds.com

ruffrecords

Re: Steel for enclosures
« Reply #16 on: March 16, 2019, 04:17:39 AM »
Thanks Bri. That seems to confirm it was some kind of cadmium or chromium treatment of inc plating. I too rememeber the coloured swirls - a bit like when you get a film of petrol (gas) on a puddle i the sunlight. I have ordered some Zintec panels to try out.

I wonder what they use these days in 500 series modules?

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

JMFahey

Re: Steel for enclosures
« Reply #17 on: March 16, 2019, 05:13:25 AM »
I commercially make Guitar Amplifiers in Argentina, for 50 years now, and always tending to make as much as possible in-house.

Among other elements, I make own chassis and speakers, from scratch.

Hate iron because of all the extra wasted time and money protecting it from oxidation, so use Aluminum for any kind of chassis, own shears, folders, punchers and lots of dies, BUT for speaker frames , magnetic circuit plates and polepieces I am forced to use steel.

My *preferred* finish is zinc plating, which I send to an outside shop.

Mind you, as with everything else I tried it in house too, so setup the tanks, got the solutions, built a huge power supply, etc.

End of the story: after 1 so-so batch and a second quite acceptable one, (practice makes perfect) I unplugged everything, neutralized solutions as suggested and threw everything away (losing quite a bit of money in the process).

*ALL*  baths use Cyanide  :o  one way or the other, and besides that I found I was holding my breath trying not to breath the fumes  :o   .... really my life and health are worth way more so I junked everything.

Sending it out is *cheap* , only problem is that finishers charge for a minimum batch, even if plating a single nail, here it´s 50 kg minimum.
No big deal for me since my batches are at least 50/100 speaker frames each, but may be a problem for a hobbyist.
That said, and "when I was a kid", I used to visit industrial shops of any kind with my project in one hand and a couple "longnecks" (fine wine bottles) or a couple sixpacks which I "carelessly forgot on the counter" ... I was always well received ans almost never was charged , my project was processed with somebody else´s batch.  ;)
Only problem is that sometimes I had to wait a week or so ... no big deal.

Pure zinc is dull whitish and not that stable, so the last bath is a Passivating solution, which both makes it bright/shiny and gives it a hue.

You can choose "Blue" which is actual silvery with the slightest bluish hue, you notice it only side by side with say, a piece of raw aluminum, or "Yellow" , which roughly imitates Chromate but is safe and accepted.

As a sample, here is one of my 10" speaker frames:







notice the slight bluish hue.
Design - Make - Service Audio Equipment since 1969.

john12ax7

Re: Steel for enclosures
« Reply #18 on: March 16, 2019, 05:31:00 AM »
I've always liked the look of the yellow zinc plating. But other than appearance, would stainless steel be a viable option since it has corrosion resistance?

Ilya

Re: Steel for enclosures
« Reply #19 on: March 16, 2019, 06:04:42 AM »
I've always liked the look of the yellow zinc plating. But other than appearance, would stainless steel be a viable option since it has corrosion resistance?

Stainless is a pain to work at hobby shop. It's probably more expensive to machine at the fab because it's so much harder than mild steel.
PCBs, enclosures and build guides at www.rackneve.com


 

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