RoHS restrictions on Hexavalent Chromium

A. Items that are 'chrome plated' (think of the brightwork on a Harley-Davidson) have their chromium in metallic form (valence state zero) whether the plating bath they were plated in contained hexavalent chromium or not. So they are not prohibited.

But items that are zinc plated or zinc-alloy plated (including many fasteners) invariably require a 'chromate conversion coating' to retard rust. This conversion coating is largely a gel that contains the original conversion coating solution; if the parts were conversion coated in a solution that contained hexavalent chromium they almost surely would fail to meet RoHS standards.

A. There seems to be a lot of confusion about the RoHS regulations. These regulations relate to the use of various chemicals in electricals and electronics. Unless the fasteners are being used in electrical or electronic goods these regulations do not affect you.

If your goods are used in the electrical or electronics industry then Ted's comments apply.

Thanks Brian. You're right that the RoHS standards may not apply to James' product line; I inferred, possibly incorrectly, that he was questioning whether the standards prohibited chrome plating.

They shouldn't affect properly rinsed chrome electroplating, which involves only zero-valent metal, but they do apply to hexavalent chromate conversion coatings, which are no longer used in the automotive industry and in other broad swaths of applications, either. Because they are probably potentially carcinogenic, and because widely accepted alternatives now exist, it's not a bad idea to get away from hexavalent chromate conversion coatings except possibly in aerospace where the need for reliability should trump all.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

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Sorry Ted,

Wasn't able to read such a specific meaning from the question and was not trying to contradict you either.

But, even in the UK, there seems to be a lot of confusion about how to apply the RoHS regulations and that they apply only to the electrical and electronics industries.

By the way, even aerospace is under very heavy pressure to lose hex chrome from their aircraft. We are a little slow in moving in aerospace, because of the safety factors involved, but we will catch up...eventually.

Brian Terry
Aerospace - Yeovil, Somerset, UK
2005

Thanks again Brian. In the interest of safety I hope aerospace never catches up. As one example, hexavalent chromate conversion coating on aluminum is highly visible, reducing the chances of an improperly prepared part finding its way into an airliner, whereas the trivalent substitute is essentially invisible.

Luck & Regards,

Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 2021

A. It may seem a trifle pedantic but hexavalent passivated finishes are prohibited in Europe for automotive applications under the End of Life Vehicle Directive(EOLVD) and on electrical and electronic equipment under the Restriction of Hazardous Substances (ROHS).The RoHS directive takes it scope from the Waste Electrical and Electronic Equipment (WEEE) directive which aims to minimise the impact of this equipment on the environment during their lifetime and when they become waste.The EOLVD has broadly similar aims.

Thanks, John, I don't think you are being pedantic at all. I think you are noting that regardless of whether RoHS specifically applies to particular components, the principle applies to a lot of components (and it will probably eventually apply to all).

But I have found that many people from outside the surface finishing field assume that chromium plating from traditional hexavalent plating baths is prohibited by these standards, but it isn't.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2005

A. to David,
The EU's Rohs requirement, It is required less then 0.1% in homogeneous material.

Here is an explanation I quoted from a training material wrote by Dr.John Lau

(1) Homogeneous material means a material that cannot be mechanically disjointed into different materials.
(2) The term homogeneous is understood as of uniform composition throughout, some examples of homogeneous materials would be individual types of plastics, ceramics, glass, metals, alloys, paper, board, resins, and coatings.
(3) The term mechanically disjointed means that the materials can be, in principle, separated by mechanical actions such as unscrewing, cutting, crushing, grinding, and abrasive processes.
(4) Using these interpretations, a plastic cover (for example) would be a homogeneous material¯ if it consisted exclusively of one type of plastic that was not coated with or had attached to it (or inside it) any other kinds of materials. In this case, the MCV of the RoHS Directive would apply to the plastic.
(5) On the other hand, an electric cable that consisted of metal wires surrounded by nonmetallic insulation materials would be an example of something that is not homogeneous material¯ because mechanical processes could separate the different materials. In this case the MCV of the RoHS Directive would apply to each of the separated materials individually.
(6) A semi-conductor package (as a final example) would contain many homogeneous materials, which include the plastic molding material, the tin-electroplating coatings on the lead frame, the lead frame alloy and the gold-bonding wires.

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'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean -- neither more nor less.'

'The question is,' said Alice, 'whether you can make words mean so many different things.'

'The question is,' said Humpty Dumpty, 'which is to be master -- that's all.'

Thanks Anderson. But actually, a "homogeneous material" means whatever they want :-)

When speaking of a steel part with zinc plating, for example, they want the steel part to be considered a single homogeneous material and the plating plus the subsequent conversion coating deposited on its surface to be considered a second "homogeneous material". This despite the fact that the chromate conversion doesn't fully penetrate the plating, so it's certainly not homogeneous, and despite the fact that a small child can easily remove most of the chromate from the zinc plating with a pencil eraser whereas a skilled machinist can't "mechanically disjoint" the plating from the steel part with any machine in his shop :-)

Retaining sanity demands that we not attempt to understand illogic, but simply accept that the European Commission is Humpty Dumpty and 'homogeneous' means whatever they choose it to mean -- neither more nor less, and they mean it to include the plating pluus the chromate conversion coating as a single item :-)

Regards,

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

A. Karen: Maybe there is a typo in your inquiry and you meant that the materials you listed are not a concern? My understanding is that the RoHS materials are lead, mercury, cadmium, hexavalent chromium, PBB and PBDE.

Thirunavukkarasu: Stainless steel and chromium plating contain metallic chromium, not hexavalent chromium.

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Ed. note May 2017: Please observe the dates on some of these entries. 4 more restricted materials were added to the prohibited list in 2015 as one example of changes.

A. Yes, it's compliant (to my understanding) because chrome plating is metallic chromium, not the hexavalent chromium that is restricted.

A. You are certainly right that you need proof rather than people's opinions, Alex. Further, if chrome plated parts are not rinsed properly, it's probably very possible for them to be shipped while containing enough dried-on hex chrome to violate RoHS standards. I know of a manufacturer of chrome plated chain saw chains who seemed to want to dry as much of the hex chrome onto the parts as practical, to minimize the amount he needed to rinse off and treat :-)

So either you or the plater probably must do sufficient testing to be able to certify the plating as hex-chrome free / RoHS compliant. Good luck.

A. Hi Riley. When someone uses the slang 'mechanically plated yellow' they probably mean mechanically plated with zinc, followed by chromate conversion coating of a yellow color. Sorry, I'm not familiar with the term "yellow 2".

Traditionally, yellow chromate was hexavalent, so parts that are several years old probably do contain hexavalent chrome. For the last 10 years of so, trivalent chromating has been increasingly common to the point where yellow parts produced today are probably most likely hex-free. But it's not guaranteed.

Regards,

A. Salutations,

An educated guess would be that "Yellow 2" would refer to ASTM B633 for Service Condition 2 (SC2) which is the harshness of the operation would related to the thickness of the coating. SC2 is for moderate exposure to corrosion and is 8 micrometer thick (e.g. we use it for a dry environment with rare exposure to the elements for parts that we desire to last 10 years as an example). Our legacy drawings do contain similar lexicon.

Following up with Ted's comment, the best way to determine the coating would / could include a letter of compliance from the plater that it meets RoHS or that it does not have a hex chrome plate.

There are test methods and labs that would be willing to test to confirm plating for chrome but may be above and beyond your desire for accuracy.

Cheers

A. I would be reasonably sure that the reference is to ASTM B695 "Standard Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel." Therein, Type II refers to 'colored chromate conversion treatment.' This standard has not been updated to reflect current trends to 'trivalent passivates.' So your deposit could be a yellow hex or it could be a yellow tri. Your plater should have the answer, but you can get assurance from the ISO 3613 (1,5-diphenylcarbazide) spot test, although it has been known to give false negatives.

A. Hi Katie. As you'll see in the thread which we attached your inquiry to, the problem is that it is the plating layer by itself, not counting the component it's plated onto, which is limited to 0.1%. The substrate is considered one homogeneous material, and the plating plus the chromate is considered a separate homogeneous material .

Regards,

A. Hi Katie,

Further to Ted's response, RoHS and REACH are very different animals.

RoHS deals with the plating as a separate article and the limits are therefore much more relevant. For commercial vehicles this regulation is rather more restrictive than REACH, but has less relevance to the Aerospace industry so my knowledge of the requirements is a little more sketchy than it should be!

REACH can have different levels of compliance:

Article 7 requires a declaration if a Substance of Very High Concern (SVHC) is present at amounts greater than 0.1% w/w in an article and that 1 tonne or greater is manufactured or imported in the European Union (EU) per annum.

Article 33 requires a declaration if a SVHC is present at amounts greater than 0.1% in an article when requested by the customer regardless of the amount produced in any one year.

A recent ruling by the European Court of Justice (ECJ) has better defined an article, the so called O5A ruling "Once an article always an article". So when your nut or bolt or washer is formed and then plated it is now considered an article and although its contribution to the total weight of the car is minimal in its own right it may require a declaration.

Annex XIV requires that any material on this list is not used after the sunset date within the EU without a valid Authorization or an Application for Authorization has been submitted.

Annex XVII is the restriction list and details what restrictions are in place for the use of certain substances.

So as you can see REACH compliance isn't quite as straightforward as it seems. There are people out there that make their living dealing with these regulations, so if you feel a little overwhelmed you may want to consider getting some advice from a consultant about compliance with these regulations.

Best of luck.

A. Joe,
Per wikipedia, "The restrictions are on each homogeneous material in the product, which means that the limits do not apply to the weight of the finished product, or even to a component, but to any single substance that could (theoretically) be separated mechanically "for example, the sheath on a cable or the tinning on a component lead."

You say your part is treated with hex chrome. This part is important, is it a treatment or a coating? Does any of that chrome in that bath stay with the part after the process is completed? If no, then the process should be considered irrelevant to RoHS. (Though you can probably find some people who will hear "hexavalent chromium" and immediately declare the whole thing non-compliant.)

A. Hi Joe. If this is a chromate conversion coating (chem film, Alodine, Iridite, MIL-DTL-5541) it will not be RoHS-compliant. You need to use a trivalent chromate or chrome free formulation. MIL-DTL-5541 [on DLA] accepts trivalent formulations; there are QPL-approved trivalent treatments.

Regards,