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"Health issues related to grinding chrome"



Current question and answers:

March 8, 2021

Q. Hi,

I'm an engineer working on a project that involves some chrome plated parts and I'm wondering about hazards that might be associated with heating those parts up to fit them to another.

The sub-assembly is a shaft and we're fitting separate bearing sleeves. The actual journal diameters have been hard chrome plated and will be ground after being fitted to the shaft.

The fit to the shaft is a fairly heavy interference fit and we were looking to heat the parts up to around 400 °C for assembly. But then someone raised a concern about hexavalent chromium and so we're trying to investigate whether this would be a hazard.

I've seen mention of hexavalent chromium being generated during welding of chromium steels and 'other hot work' but am struggling to find out at what temperature this becomes a concern, and whether there are other factors that come in to play. One web source mentions calcium containing materials can be a factor and we're not certain of the composition of the insulating bricks that might be used to support parts during heating.

Is this a valid concern? Or am I jumping at shadows?

Any help would be appreciated,

Regards,

Doug.

Doug Rawlings
- Worthing, UK
^


57138-1
March 2021

A. Hi Doug. My personal belief and limited experience is that 400 °C isn't all that hot. I imagine chrome plated motorcycle exhaust systems get hotter, and continuous casting molds in steel mills much hotter. Myself, I wouldn't worry about it ... but there's a difference between personal philosophy and offering advice for others :-)

I think we've entered a time where, assuming this is not a one-time assignment, testing rather than guessing is probably called for. If it's a one-time thing you should probably read the current regulatory thinking -->
... and decide from that that whether you feel there is no reason for concern, or decide to be super safe by wearing a welding hood, respirator, or other protection.

Luck & Regards,

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


April 7, 2021

Doug,
I remember seeing some paper that after heating to few hundred degrees C, the plated Chrome slightly reduces it's hardness, and at higher temperatures above 600-700 °C it may be oxidized (probably creates some Cr-hex products)

So, your 400 °C looks like a safe zone (unfortunately I cannot find that paper).
Best regards,

Leon Gusak
- Winnipeg, Canada
^




Previous closely related Q&A's starting in:

January 26, 2009

Q. I am the EHS (Environmental, Health & Safety)representative of a mold-building shop. The production foreman asked me if it's safe to machine and polish blocks of steel that have been plated with chrome. Since the plated chrome is derived from the hexavalent, Cr(VI), chromic acid, I'm a bit concerned with potential inhalation hazards (the exposure limit is extremely low).

Jeffrey Murphy
Machine shop - Rogers, Minnesota, USA
^


simultaneous January 27, 2009

A. It does not matter what the chrome is derived from as long as it is chrome metal it has a valence of zero and is thus safe to grind with normal grinding precautions.

James Watts
- Navarre, Florida
^


January 28, 2009

A. Jeffrey,

As plated chrome is in the 0 valence state. The only way there could be any hexavalent chrome present is if your platers have rinsed the parts very poorly and allowed the hexavalent chrome dry on the parts. This will be fairly obvious as the hexavalent chrome will be a red/brown colour, the as plated chrome should be a silvery shiny metallic colour.

Brian Terry
Aerospace - Yeovil, Somerset, UK
^



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



May 10, 2011

Q. I am a safety manager for an injection molding company. My tooling group grinds and polishes chrome plated parts everyday. I was recently asked to acquire a respirator for one of these gentlemen that claims he had to wear one when he worked in CA for a metal finisher. I have searched OSHA's web site for help and do not see much. They talk about Hexavalent Cr but mostly in the plating of metals not in the polishing and grinding.

1) Is there a health risk from exposure to Chrome polishing and grinding?
2) Can some one point me to a guide on how to best protect my employees?

Steven Knapp
EHS manager - Evansville, Indiana
^


simultaneous May 12, 2011

Proper grinding of chrome uses so much grinding (cutting) fluid that there should be zero problem from the chrome. Fluid mist inhalation might be a problem, but chrome would not be.
I seriously doubt if polishing would be an inhalation problem, but could be.
Keep the employee happy. get him whatever mask he wants, but tell him that there is no OSHA requirement for it. Make him responsible for keeping it clean. Do not give him a respirator or you will be liable for a horrible amount of record keeping and controls.

James Watts
- Navarre, Florida
^


May 12, 2011

If it were me, I would not want to be potentially inhaling any hex chrome particles resulting from a polishing operation. As long as the polishing process doesn't generate any fumes, a simple dust mask should be adequate, and are relatively inexpensive when compared to the price of a half-mask respirator with canisters.

If you'd really like peace-of-mind, (and also CYA for a potentially disgruntled employee) you could have several employees wear air monitoring devices during a typical workday, and send them out for analysis. This may not be cheap..but would insure that you know whether your employees are or aren't exceeding the TWA limit for exposure to Hex Chrome.

Marc Green
Marc Green
anodizer - Boise, Idaho
^


May 12, 2011

You're right, you do not have hexavalent chromium and that makes it a lot easier for you. You should do the industrial hygeine monitoring and see if your employee exposure is under the permissible exposure of 1 mg / m3 as a chromium metal dust. Chances are it will be much below that, but you need the data to prove it. Your local safety consultant should be able to get the test set up for you. There are likely other tests that you need to do as well as evidence that you are exempt (or not) from OSHAs respiratory protection standard.

Jon Barrows
Jon Barrows, MSF, EHSSC
Independence, Missouri
^


simultaneous May 13, 2011

A. Steven,

It seems that there is some confusion as to the oxidation state that your employees are handling.

When working in a finishing shop the solution used to plate chrome is hexavalent chrome (chromic acid) and if controls are not adequate to control exposure to the hexavalent chrome then severe safety measures have to be taken to prevent exposure. Hexavalent chrome is nasty stuff, carcinogenic, toxic in its own right, sensitising to both skin and lungs, can cause "chrome ulcers" and so the employee is right in that case.

When you plate chrome you change it from hexavalent chrome to metallic chrome (for want of a better thing to call it let's call it chrome zero). Now chrome is actually one of the essential trace elements that we all need to survive. It is not classed as toxic, but the dust can be considered a nuisance dust if the grinding operation is generating significant amounts of dust. I would suggest in this case that a dust mask is more appropriate than a respirator.

Brian Terry
Aerospace - Yeovil, Somerset, UK
^


May 13, 2011

Q. Does the chrome change its state to a lower value once plated (i.e., hex to tri)?

Sorry, not real familiar with chrome plating, other than the general process.

Regardless though, I would think one would want to wear a dust mask if any type of metal particles/dust are airborne in potentially large qntys.

Marc Green
Marc Green
anodizer - Boise, Idaho
^


May 16, 2011

thumbs up signThanks for clearing that up, Brian. That's 2 things I've learned from this board in the matter of a week or so!

Marc Green
Marc Green
anodizer - Boise, Idaho
^


May 16, 2011

A. Hi, Marc. The state changes to zero -- neither hex nor tri.

Regardless of what material is causing a dust or grit or smoke in the air, though, our lungs were not designed to inhale it. A dust mask or better should always be worn if anything is in the air, whether it be chrome or sawdust or truffles.

Regards,

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


May 17, 2011

A. The OSHA PEL for chromium metal as a respirable dust is 1 mg/m3, whereas for hexavalent chrome it is 0.005 mg/m3. So it is obviously much easier to be compliant with chromium when it is only present in the metallic form. Any respirable dust is hazardous to some extent, but unless the air is visibly cloudy from all of the dust, it is not likely that you are near the PEL. Still, OSHA likes to see data as proof which means that you should do your industrial hygiene tests. As long as your process doesn't change, you only need to do it once.

Jon Barrows
Jon Barrows, MSF, EHSSC
Independence, Missouri
^


June 27, 2011

A. Hi,

I absolutely agree with Ted and others having responded to this subject, however, I am quite surprised that it is still not "Standard" using masks in any work which relates with Dust, Fumes, etc. even while within limits of OHSA.
Sadly but true, saving on the wrong spot.

Kind regards,

Dominik Michalek
- Sydney, Australia
^


June 27, 2011

A. Opinions may flood the page but still bottom line, Jon Barrows hit the nail right in the head. In terms of safety and health get the facts and comply with the law.
G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico
^


thumbs up signHi. It's going to be one of those rare occasions where I must disagree with Guillermo...

Of course we have to comply with the law -- it's the law. But we can have opinions that differ from the law, and when those opinions suggest that legally mandated practices are inadequate, we should try to pro-actively go beyond them to the extent that the law doesn't prohibit it. Silent Spring would never have been published, and probably the whole environmental awareness movement would have been seriously delayed, had Rachel Carson not had the gumption to tell us how dangerous the bureaucrats were with their carpet bombing of our towns with insecticide and their other foolish but legal practices.

Asbestos is not chemically dangerous to my knowledge, which may be why there were not adequate laws to protect workers from inhaling it. If people had simply accepted the general advice that crap doesn't belong in our lungs, whatever it is, the asbestosis tragedy might have been greatly mitigated.

Closer to home, hexavalent chromium fumes weren't considered carcinogenic until fairly recently, even though we all knew that they were very harmful. I had a terrible row with an architect who insisted that a large canopy exhaust over the whole line, instead of local lateral exhaust, was adequate for a chrome plating line because there were at the time no rules against it.

So I'm going to insist: no solid particles of anything belong in your lungs, which means you should be wearing some sort of dust filtration device if there is any evidence of dusting.

Regards,

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



January 11, 2016 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Can someone tell me if grinding (without a mask) a chrome plated replica 8 inch non firing gun barrel would be dangerous??
Does the chrome plating become hexavalent chromium when I cut it? Or is this Chrome plating called trivalent chromium? I have heard so many stories about the "dust" and or "filings" that are on the floor that I am unsure of anything now. Thank you.

Robee Briggs
- Gold Coast Australia
^


January 2016

A. Hi Robee. Chrome plating is chromium metal, valence state 0; it's neither trivalent (valence state +3) nor hexavalent (valence state +6). Chromium metal is not chemically dangerous; chrome plating is used on various kitchen and serving equipment.

But if you are seeing dust and filings in the area, you should consider wearing a dust mask because that kind of garbage doesn't belong in your lungs (or your stomach). Good luck.

Regards,

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

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