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topic 38047

Horizontal hard chrome plating plating vs. vertical


A discussion started in 2005 but continuing through 2018

2005

Q. Hello,

My name is Neel. I am a part time researcher. We are a team of 4 researchers. We are helping a small entrepreneur in his research. He is a manufacturer of hard chrome plated bars and tubes.

1) We wanted to know the advantages and disadvantages of horizontal hard chrome plating over vertical hard chrome plating. The length of shafts is around 3-3.5 meters and plating thickness desired is 20 microns.

2) In the conventional vertical bath, we are getting plating taper at the bottom end. What is the reason for that?

3) Will there be any time saving in the horizontal bath?

Please help me with these 3 questions.

Regards,

Neel Pandya
researcher - Pune, India


2005

A. Neel,
As a researcher you know that it makes a job easier when you are in possession of all the facts. Unfortunately, you are a bit vague as to what is being done by way of materials and processes.

As far as your points are concerned, regarding the orientation of a tank, horizontal tanks of this size will take up more floor space and will be more prone to solution evaporation. You will also have increased issues with fume extraction using horizontal tanks. In practical terms, the lower the exposed surface area of a tank, the easier it is to reduce losses, but there may be other effects you may want to minimize, such as foaming; a small surface area but high charge density per unit area could result in an unacceptable foaming level. With regard to the second point, I assume you are using hexavalent chromium and therefore suspect you have a problem with jigging - a 3.5 meter tube is one hell of a length to throw with chromium. You should consider using multiple connections onto the tube. As far as time is concerned, like all electroplating, Faraday's Laws dictate how much metal is deposited; the trick to success is to use Faraday's Laws to your advantage and to maximize deposit uniformity and minimize any electrochemical losses and wastage.

trevor crichton
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK


2005

A. Both arrangements are in very widespread use. Neither horizontal nor vertical is "better" -- each has advantages and disadvantages that can be weighed for the particular circumstances.

One potential advantage of horizontal plating is partial submersion so that you can measure the plating thickness and spot some gross defects as the plating is progressing. Another is much shallower tanks and more practical building shape

Advantages of vertical plating include simplicity (no need to rotate the shaft during plating), and much lower floor space and fume emissions.

Ted Mooney, finishing.com Teds signature
Ted Mooney, P.E.
finishing.com - Pine Beach, New Jersey
Striving to live Aloha


2006

A. Neel,
I read the Trevor and Ted's answer, they are good, but I would like you to know some practical points for this problem.
At first, there are some differences between these two procedures. Based on Cr(VI) plating, I can guess how do you it, but I don't know your equipment level. If I assume your solution was refined and with a normal condition --
1- Could you balance the temperature between bottom and top of the bath during your plating? For this tank, it's more important to getting a good result in the vertical and with this depth.
2- Do you have a fixture for preventing going near the anodes with the shaft at the bottom of the tank, or another mechanism for this?
3- With this vertical procedure, you had anodes about 3.5 meter minimum, were your anodes clean at all of this surface (for example at the ends of it).
Regards,

Hamed Shams
- Karaj, Iran


July 25, 2009

A. Neel:
Based on the answers you have received and the absence of this problem on the Internet, I can only conclude the parts can be plated vertically without taper. With a single connection at the top we had the same problem; and after checking everything we concluded the taper was due to voltage drop and thus less current density from top to bottom. However, like you, we are not certain. Copper core anodes possibly help but resistance in the part is still present with no practical way of multiple connections.
Can't see horizontal improving taper except anode current distribution potentially improved.
I hope we hear more on this.
Cliff Smith

Cliff Smith
- Oklahoma City, Oklahoma


August 18, 2010

Dear Neel,

1) We wanted to know the advantages and disadvantages of horizontal hard chrome plating over vertical hard chrome plating. The length of shafts is around 3-3.5 meters and plating thickness desired is 20 microns.

Major Advantage of horizontal Plating Equipment:
- Highest Metal Distribution along the whole length of the bar
- No impact of varying anode position
- Stable plating conditions

2) In the conventional vertical bath, we are getting plating taper at the bottom end. What is the reason for that?

-Already answered by Cliff

3) Will there be any time saving in the horizontal bath?

-YES: due to better less overplate and higher current density, horizontal equipment is more cost effective.

Dirk W [last name deleted for privacy by Editor]
- Hamburg, Germany


Hard chrome horizontal tank

August 6, 2018

Q. Hello,

Most hard chrome processes that I encounter are carried out in vertical tanks, mostly because of dimension of the workpiece and the ease of ventilation, heat loss, etc.

What if I need to carry the process in a horizontal tank? I struggle with the issue of suspending a workpiece in the process tank. How to solve the matter of anodes and auxiliary anodes?
Does the workpiece need to be completely immersed? If so, does it need to rotate between anodes?

Thank you for your support

Lucas Potocki
- Bydgoszcz Poland


August 2018

A. Hi Lucas. During the second world war, driveshafts for ships were sometimes conveyed to railroad sidings inside or next to chrome plating shops on flatbed cars for replating. In some cases, horizontal plating tanks were built on site on the railroad car and the shafts were plated without removing them. Necessity is the mother of invention. The platers who told me about this have all passed on and I've only seen pictures and sketches, but smaller scale, less ad hoc, horizontal plating is certainly still done.

For horizontal plating, the shafts are usually only partially submerged and constantly rotated. I think it is necessary to keep the portion which is out of solution wet. If you patiently search old journals and patents you should find some info.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
finishing.com - Pine Beach, New Jersey
Aloha -- an idea worth spreading


September 7, 2018

A. Hi LUCAS, both techniques have their own plus/minus. All depends on job shape, quantity to be plated per batch and the uniformity of coat required.
A picture speaks louder then words. If you have a problem plating a specific part post a pic here; I am sure many experts here will be able to help you out.
I have plated long parts horizontally and small parts vertically in a horizontal tanks with success.
All the best.

vikram dogra
Vikram Dogra
Irusha India - Chandigarh, India


May 19, 2020

A. Hi Neel, one thing used to fix the taper is baffling material, so protect the job with a non conductive material to shield it from the anode if your anode length is longer than the job. Another way is with the anodes shorter than the job to stop the high current density areas having a massive effect; plating tanks are meant to be designed that way, even though commonly they are not. There are other practical things you can do to reduce the effect of the tapers. Do have in mind that for heavier chrome deposits, beyond just a flash of a few thousandths or microns, the problems of an uneven deposit will occur even with precautions in place.

Q. I am actually trialing horizontal chrome plating now at work and we are curious how the chrome is effected with the job being out of solution, knowing that chrome needs an under 5% ripple rectifier to produce an adherent bright deposit.

Lewis Brierley
- england

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