Knife coatings. Are they Safe to Use With Food? What do we know?
Before reading any further, if you ARE definitely concerned/worried about what types of coatings are food safe then I strongly recommend you to ONLY use UNCOATED and obviously give up smoking and drinking and any other unhealthy activities such as recreational drug use etc. and you can also stop reading any further, since you will need to spend a lot of time getting your body back to temple mode (shown below LOL).
Example knife: A totally food safe uncoated 440C steel blade from Cudeman in Spain.
If you are NOT definitely concerned but want to know more, then please read on.
DISCLAIMER!!!! You Must Read This!
*You should note I am not advocating that coated blades shown on my social media channels or here on this blog or any social media that I post stuff to, are food safe. "It's do as I say, not do as I do"!
That being said there is a huge difference between cutting blades coming into constant contact with food stuffs of all pH ranges 24/7 such as in food processing plants, where one will find the majority of such blades are uncoated and coated blades encountering food stuffs on an infrequent and short term basis of which no reliable data exists for the latter, in terms of harmful products being either released as a result of volatile/leachable emanations from the materials used in the coatings and or fragmentation of particulate matter and contamination of food stuffs.
The only true food safe knives are those which are UNCOATED. Why do I say this? because for all food safe testing of (at present, polymer based compounds) materials in contact with food items, then time of contact and pH conditions are also key factors in determining whether an item can be designated food safe for it's intended application/s.
To understand whether a coating is considered toxic to human health requires stringent experiments to be done in the most realistic laboratory conditions in order to make meaningful conclusions; in other words obtaining data from properly designed experiments. If this is not conducted in such a way then one can not arrive at any sensible conclusions and it is ONLY PSEUDOSCIENCE at best!
"Toxic" what does it mean?
Foreign substances can be toxic in many ways. For example:
Chemically, where there is a direct interaction from said chemical and some biochemical/physiological process (such as simply binding to some biomolecule) , for example: the action of cyanide on the transport of electrons in the electron transport chain where cyanide blocks Cytochrome C oxidase transporting electrons. No electrons to Oxygen the final electron acceptor,(yes, the only reason we need oxygen to live) and hence no ATP production (ATP being that energy source we all need to live. Result, we will die from cyanide poisoning without serious medical intervention.
Binding and changing how something functions, yes it can be a big big problem for the human body. Other types of toxicity may arise from a physical interaction or interference,
Something being where it shouldn't be and more than often causing an abnormal cellular response, detrimental to the proper functioning of the cell/s in question.
This is one of many concerns for "nano particles" and is beyond the scope of this article but I need to mention it here. Although I give an example that almost everyone is aware of:
Coal miner's lungs and cigarette smoking (both involving particulates and chemical interactions of particles on the nano scale).
One must exercise great caution these days when consulting the internet for information.
Something to note before I leave the subject of nano particles:
For example: the AI generated answers to the following question regarding health issues from DLC (Diamond Like Carbon) coatings; I posed the following search inquiry/ question:
"DLC particles harmful to health scholarly articles"
The AI returned much information unfortunately it was equivalent to the "lazy student" who actually, not only didn't read the question properly but who also produced erroneous results by confusing what they had read and then written with great authority their summary!
Under it's listed results I followed a link which was produced by the AI to the following paper (and found it wasn't a scientific paper at all but more of a journalistic sensationalistic-ally titled:
Unseen But Dangerous: Understanding the Health Risks of Ultrafine Particles in Ambient Air .
This reference had absolutely nothing to do with DLC as I soon learnt by following the next reference which was the actual paper discussing neurological effects (NOW this IS my area of expertise as a scientist)-lucky me!
Ok the authors of this 2008 paper, Calderon-Garceduenas et. al. 2008 entitled:
Air pollution, cognitive deficits and brain abnormalities: A pilot study with children and dogs
Appearing in the journal Brain and Cognition
Vol 68 Issue 2 2008 pp 117-127
had absolutely NOTHING to do with DLC coatings and toxicity! See how the AI works! Beware of false information and obviously to cover themselves the creators fo the AI even state it can return erroneous information!
I wouldn't say erroneous, I'd say more like as I stated above; the AI took the lazy and clumsy approach of which a "real student" might take for such a task (In my many years experience at universities globally). This is how information gets twisted and ends up simply "Fake" but then this "Fake" information somehow becomes dogma!
Let's continue......
We've all heard or know how radiation can be hazardous, there are physical/chemical interactions and also ones of straight chemical toxicity; for example the radioactive compound Uranyl acetate, a commonly employed radioactive heavy metal electron dense stain in the preparation of biological samples for routine electron microscopy is extremely chemically toxic as it binds irreversibly to nucleic acids- yes, your DNA!
Working with this compound for almost 20 years I was of course very cautious because of it's radioactive hazard however, the true hazard is it's chemical toxicity. In fact there is a common joke, if you like, amongst biologists who are NOT involved in biological electron microscopy, that they could not be paid enough to work in such laboratories with the plethora of toxic compounds in routine daily usage !
Another killer in clumsy hands in the same laboratories is Osmium tetroxide. However, none of these deadly (and they are) chemical compounds are killing off electron microscopists like no tomorrow because these people are employing strict codes of safety in the work place.
Now this brings me way back to knives and the coating of knives. What do we know? We know there are currently several types of coating applied to metallic surfaces. They are (and not limited to):
Fluorinated hydrocarbons such as (TEFLON) PTFE (TEFLON) FEP, (TEFLON) PFA, (TEFLON) ETFE.
Don't forget TEFLON is a BRAND, NOT some chemical formulation!
These products, before application ie raw materials are either solvent based whether that solvent is aqueous (water) or organic solvent based or in a powder form. There are at least 15 different types of fluorinated hydrocarbons under the trademark name of TEFLON- XXX etc. Bear this in mind!
Application methods range from various forms of painting techniques to electrostatic applications and may either involve one or two steps. Here I will refer the reader to this reference.
What is clear from the literature such as MSDS sheets (that is Materials Safety Data Sheets)-legal requirements in all legit countries and operations globally), is that the raw materials for such coating should be treated with strict safety measures to avoid human contamination or the production (and then human contamination) from combustion products. As for fully cured compounds, again unless categorically stated from the manufacturers literature, should NOT be taken as food safe especially when it comes to coatings upon knife blades.
Most MSDS sheets will list all known hazards such as, is the compound carcinogenic and what are the target organs within the human body etc.? How flammable etc etc.? I will not try and cover these types of documents, as the jargon is not for the lay person but that of the biologist and or chemist or specialist technicians handling and working with such raw materials and or finished products .
Suffice it to say there are clear warnings on these documents which will either describe a warning or other safety cautions when it comes to the effects upon humans. They may not indicate whether something is food safe but rather list the raw ingredients and whether they by themselves are hazardous to human health in some way. As for literature on fully cured compounds, there is little, however I refer the reader to the following out of interest.
Unfortunately, as mentioned, many manufacturers of knives refuse to disclose what types of coatings they are employing and or whether they are food safe or not, simply falling back upon, "they are IP" and "We are not at liberty to divulge their composition", or under the best scenario, categorically stating they are NOT food safe.
Some remain silent on the subject and of course this can be understood as fear of litigation is a real threat as they have no control over the myriad of substances which may come in contact with their products which could pose a threat to human health but not be as a result of coming into contact with food stuffs which are later encountered.
That's perfectly ok because it would be a totally marketing feature and benefit to list a knife coating as "food safe" and the fact that it isn't stated, definitely means isn't food safe or the product is yet to be tested (if ever) to see if it meets FDA requirements for food safety and or for safe contact with foodstuffs. It's complicated!
In reality
So I'm certain that in the history of the global usage of coated blades, someone at sometime has used their knife to cut up some food. Certainly this has not been conducted with the frequency of what a chef would be doing in a busy cafe/kitchen or restaurant. Whether that coated blade was designated "Food Safe" is highly unlikely and the said operator struck down with health issues arising directly from cutting up some food with the same knife, is also highly debatable not to mention extremely if not impossible to determine, if not foolish to even consider such a scenario, for this would imply a blade coating is so deadly that even merely touching it would bring down the curtains and that's pure nonsense.
Let's looks at some facts
Generally, TeflonTM as in TEFLON PFA is considered food safe if not heated above 200C. Hence manufacturers of TEFLON (this is a trade name for several fluorocarbons including PTFE) recommend NOT heating your TEFLON food grade coated cookware above 200C.
It's unlikely for one to be heating theoretical TEFLONTM coated outdoor knife blades above 200C unless one wants to destroy the temper of that knife! So therefore any toxic related compounds from pyrolysis (fancy word for breaking down under heat) could not be generated.
However what other things could provide a toxic insult to the human body from a coated knife blade? Well it could be any residual products slowly leaching from the application techniques. What these compounds could be, is not in my area of expertise. It could be physical particles of said compound entering the body as a result of abrasive forces or simply the breakdown of the surface coating over time or due to chemical breakdown-yes fluorinated hydrocarbons are extremely resistant to many chemicals but the key wording is "resistant" NOT "impervious". Ingestion of food grade TEFLONTM` (as accidentally abraded from cookware surfaces by clumsy cleaning) is probably harmless judging by the fact that TEFLONTM coated cookware has been around for 60 plus years, I myself (yes anecdotal of course) grew up in such a household and I'm probably more at risk from passive smoking than any ingestion of TEFLONTM particles! Also there is firm data suggesting that the ingestion of food grade TEFLON material poses no threat to human health. You can check this by searching such sites as:
Toxicity may arise from the contact period with said coating/s interacting with bodily fluids etc. hence the strict precautions when using TEFLONTM based medical implants.
What of the other popular fluorinated hydrocarbon formulations? (see this site for more information)
Here I will list a URL where one can find many MSDS sheets for popular non IP TEFLONTM based products
Black Oxide Coatings
Chemical formation of semi protective oxides, such as "Black oxides". it is possible during the formation of such oxide to produce toxic Cr ions
Figures (A-C). X25 magnification light micrographs Black Oxide coating to MilSpec 13924 standard after one year of intense field usage.
Many metallic items used in military activities have their surfaces "Blackened to a Military standard surfaces.
Such a military standard is listed here: for MIL-DTL-13924D
The "toxic concern" for black oxide coatings is the production of the hexavalent Chromium ion during the multi-step process of creating certain black oxide coatings. Cr6+ is a known human carcinogen , specifically but not limited to lung cancers. It is water soluble and can easily cross the cell membrane and bind to DNA.
What are the laws within the EU?
As of the writing of this article, there is supposedly a ban as of April 2025 on the use of hexavalent Chromium, however, this ban does not include the use of this treatment for the blackening of knife surfaces within Europe. You can easily read this document here and it specifies what exemptions there are. So in reality there is NO ban despite the know carcinogenic effects.
How about the USA?
There is an absolute tonne of material here, however it appears in reality there in no real ban either merely safety precautions.
It should be noted that it has been known for well over 60 years the effects of Chromic acid (H2CrO4) treatment on increasing the corrosion resistance of the surface of steel. See reference:
202, 1329–1330 (1964)There are possible alternatives such as this.
SO
Let's see how this toxicity is brought about.
Appearing in the: Journal of Environmental Science and Health, Part C Toxicology and Carcinogenesis
Vol. 40 2022 Issue 3-4 pp 282-315
Where does the risk come from when certain black oxide coatings are applied to metal surfaces? According to Military standards MIL-DTL-13924, which is a mainstay for finishing un painted stainless and ferrous steel surfaces used in the military. Such componentry can be but not limited to: fasteners, weapons surfaces such as firearms and knives and other mechanical apparatus. As part of the process, a chromic acid (H2CrO4) wash is performed in an attempt to increase the component's corrosion resistance.
It is prudent to note that Black oxide coatings alone serve very little in increasing corrosion resistance and are usually applied in order to reduce and or eliminate surface reflections.
The valency of the chromate ion in this form is +6 as remembering from high school basic chemistry 2X +1 (H) + +6 (Cr) = +8 and +8 + 4x-2(O) = 0, ie a neutral state.
There are currently 4 basic types of black oxide coatings coming under the banner of MIL-DTL-13924D specifications, they are:
1/ An alkaline oxidizing process performed on wrought products, low alloy steels, malleable irons and plain carbon steels.
2/ Alkaline chromate oxidizing process used on corrosion resistant steel alloys whose tempering temperatures are under 900F/482C
3/ Fused salt oxidizing process for corrosion resistant steel alloys whose temper temperature exceeds 900F
4/ Alkaline oxidizing process on "other" corrosion resistant steel alloys. Note: Only class 4 black oxide treatment is based upon performance requirements , all other treatments are from 1-3 are based upon subjective criteria. ONLY treatments 1-3 use a hexavalent chrome post treatment as mentioned above.
The use of hexavalent chrome treatments are based upon outdated documentation, as it is long since known that not only hexavalent chromium ion is a human carcinogen but also Chromates, chromic acids and chromium trioxides are toxic and carcinogenic (refer to above schematic cell diagram)
As it is not practical from legal standpoints to obtain the specific oxidizing processes according to Military specifications 13924D from any one manufacturer, it is safe to assume that no black oxide treated knife blade coming under the banner of Mil Spec 13924D should be used for food preparation (unless an emergency situation OR stated otherwise by ANY manufacturer). As to any residual hexavalent Chromium ions present post treatment (because there are many washes involved post treatments applications, it is highly unlikely any manufacturers actively assay for this on a routine basis if conducting a chromic acid wash in their black oxide steps, along with the fact that the intended end use of such blackened knife blades is military usage and not for civilian use and certainly not intended for food preparation.
If you are now paranoid there is no need to be. I simply thoroughly wash my blackened blades prior to using them and then use only vegetable oils to fill the microscopic voids in the oxide coating. I know this is not the best type of oil because it will gum and make a mess if the knife doesn't get used on a regular basis but if you do use it regularly then it isn't a problem. REMEMBER This process does not guarantee the blade is food safe and what I am doing I do under my OWN responsibility. No different to for example: "I drive fast does not mean it is safe or legal for you to drive fast".
The question is: Is there residual hexavalent Chromium present in the black oxide treated surfaces of knives? Who knows, as this appears yet to be tested.
The immediate risk from such ions are to the workers involved in the blackening processes according to the MIL-DTL-13924D specifications if not undertaken with appropriate safety precautions.
Further reading on this subject of hexavalent Chromium can be found here although I have not verified any of the reference sources.
Other Types of Blade Coatings
Substances applied via the physical vapour deposition technology. (PVD aka sputter coating)
Heat curable Ceramic based polymers such as Cerakote (see my highly read blog on Cerakote
Powder Coating- a common heat curable cheap coating (available in numerous colours) as found on many non stainless ie zero chrome steels like 1095 SK85 1055 etc. Powder coating, once very popular with a range of many colours, tends to easily wear. See this MSDS data
and see here, specifically page 47 under the title "Foodie"
Surface Burnishing Treatments (these are not by definition coatings at all) however they may have been treated by a manufacturer with toxic weapon lubricants prior to shipping. When in doubt check it out! (meaning you should consult your manufacturer if you are that concerned).
Porous coatings or Scratched uncoated surfaces can harbour bacteria and fungi.
Porous surfaces, whether from excessive scratches or a porous black oxide coating can pose a "toxic hazard" merely by providing hiding places for potentially harmful microorganisms. This situation of course can be negated simply by keeping cutting tools hygienically clean.
BTW all knives featured here there have been done extensive reviews on by BushCampingTools.
FKMD Panabus shown just before giving this pineapple the chop chop treatment before consumption! (Un-specified Teflon coated Blade).
I've lost count of the number of times I've read, heard or watched somewhere, that fluorinated hydrocarbons are secretly killing us, specifically the PTFE compounds in Gortex jackets etc etc.
There is/are NO scientific scholarly articles to suggest this and 100% of videos purporting to this fake news are cleverly disguised marketing material from competitor manufacturers.
How clever? Well, by using social media gurus to introduce their "scientific evidence" via their popular YouTube channel/s all the while wearing the competitor's clothing/apparel!
As a scientist who has published widely and spoke at many International conferences in the field of medical science, I watch and or read these articles with justified scepticism.
TEFLON TM Cookware has been around for almost 70 years. Of course this does not mean that just because something which has been around for a long time circulating within the public is safe and many chemical compounds have over the years been removed and or restricted from public usage once scientific evidence came to light in regards to potential or proven health issues which have arose after long term reliable data has been obtained.
I say "issues" and not "hazards" as something hazardous can indeed be encountered completely safely if used in strict accordance with the manufacturer's safety instructions eg, "The Fine Print". This is exactly the case for many pesticides. However, this is a totally different subject matter of which I will not write about here.
I would like to address the use of fluorinated compounds in use for the coatings of knife blades used in the outdoor and tactical areas, as clearly those used for the cooking industry are food safe (if the manufacturer states this); where such blades may come in contact with food and to see if scientific evidence in the form of peer reviewed scholarly articles are present suggest potential health hazards. There are no papers!
Now the only way to determine if a knife coating is food safe according to local laws, is of course to ask the manufacturer this question. Simply because that's where the facts lie, not on some unsubstantiated social media posts. So unless the manufacturer states that the coating is food safe then it can be taken as it isn't.
Here are 2 manufacturers I asked to speak to me about their products in regards to food safe coatings. I think that it can probably be taken to be similar responses from most manufacturers who apply coatings to their blades.
Many knife manufacturers have proprietary Teflon formulations and or application techniques.
Example 1:
For example but not limited to: coated products from Halfbreed Blades, who produce some exceptionally hard wearing Teflon coatings in my experience.
This Australian company manufacturers many excellent lines of "coated' and "uncoated blades".
Their Teflon coatings are in fact proprietary coatings and as such I can not reveal their formulations as this information is not available to me. Suffice it to say that these fluoropolymer coatings are not food safe according to them.
However, they do produce certain product lines which either feature a food grade/safe PVD coating or no coatings at all (obviously food safe) for those who absolutely insist upon this for their outdoor/ tactical knife. For example their CPM 3V knives are uncoated and there is a late model (2025) uncoated CPM 3V version of their large Bush Knife to cater for those who must have a food safe knife. They also make an uncoated San mai constructed MIK-03P GEN-2 (San VG10), suitable for hunting and all food preparation.
As this company specialises in combat and tactical tools, food safe coatings are not the norm here and this also applies to other such manufacturers with similar end use product lines.
Example 2: Extrema Ratio S.R.L. Italy
A well established Italian company who needs no further introduction. All coated products are not recommended for use with food.
Including both Black oxide treated surfaces, TEFLONTM formulations and burnished surfaces (because of treatment with weapon grade lubricants). The latter example surfaces will contain weapon oil to help preserve the surface finish and aid against corrosion.
Uncoated satin finished blades are however food safe.
Usually but not always, if the chrome 3+or 6+ ion is present in certain colour Teflon applications (according to MSDS data for the raw materials) then it is automatically designated NOT food safe. It is important to remember that even some black teflon coatings can contain the chromium ions (not just green coatings).
To summarise, the majority of food safety data comes from either raw materials and what is known from toxicological data combined with "food testing" and there is a total dearth of information regarding cured compounds on knife surfaces in terms of meeting food safety requirements.
Over the years on BushCampingTools, we have featured numerous uncoated blades of all types, all completely food safe.
Yes, you have also seen me prepare foods with some coated blades although this has never been an endorsed practice. I have also prepared many food stuffs with PVD coated blades as well, such as DLC materials.
Many types of coatings applied via the process of Physical Vapour Deposition (PVD) are food safe (See here), however it is, again important to check with the manufacturer to confirm or refute this, if you must know.
So what is Food Safety Testing?
Ok before embarking on explaining food safety testing, experimental data from toxicological testing must have first been conducted upon the said materials under question which would come in contact with food stuffs. For example for a "plastic item": toxicology tests of raw materials Vs a final polymerized product.
Migration tests
How are such "food safe" tests conducted?
Answer: In an extremely complicated way! Seriously, there are numerous test protocols involved when it comes to determining whether some item in contact with a food source (solid or liquid) is food safe or not. The listing of these protocols is beyond the scope of this article, however, here is a very brief summary of the processes involved:
Tests are conducted in order to determine under the "worst case scenario" the potential for any constituents of food contact materials (for example some polymer eg a plastic spoons /cutlery) to be transferred into a food matrix. The extent to which this/these substance/s migrate depends upon their chemical nature, the nature of the material/s from which it could be released and of course the type of food for which it is in contact.
For example there is a list of all of the monomers and additives permissible to be used in the manufacture Plastic FCMs (Food Contact materials), of which these chemicals substances could be found in the EU Plastics Directive. it should be noted for the coatings involved in the knife industry, such list of additives etc. are NOT available and often can be seen as IP and thus are not listed in MSDS data sheets.
Food Safe does not mean zero transference of any chemicals into the food item, it merely refers to a "migration limit" as determined by previous toxicological assessment.
How is Testing Conducted?
1/Tests on the food directly.
2/ Food contact materials can be tested (at migration levels which "could cause problems") prior to contact with any food stuffs to examine for leachable substances and or residues from manufacturing processes.
3/ Thirdly ("unique for materials to be in contact with foods") the articles intended for contact with food can be tested by conducting experiments with substances which represent the intended foods, for example to test the effects of acidic food stuffs, the compound acetic acid (at 3%w/v in an aqueous solution) - designated "Simulant A" would be employed.
For looking for chemical substances in meat (from any zoological source), "Simulant D" which is refined Olive Oil, would be employed as the substance to be in contact with the said materials to be tested. In the case of testing food safe products used in the dairy industry and or in contact with dairy products, 50% aqueous w/v ethanol solution is the representative of Simulant D.
As mentioned above, the purpose of the simulant is to mimic the food stuff and under worst case conditions. Of course a critical factor in all of these tests, is exposure time. For example, brief encounters on plastic surfaces such as cutting boards Vs long term storage with the same polymer.
Time constraints, for example, 15 minutes of "cutting food" exposure on plastic cutting surface of a "chopping board" would be considered a reasonable duration for the test.
The simulant would then be assayed to determine if there was the presence of any chemicals arising from the said test materials. The range of analytical methods are too broad for this essay. However, I will mention one possible analytical technique such as but not limited to: Gas Chromatography and other variations involving this methodology.
The mode of contact is also tested via the "worst case scenario". For example when testing cling films, despite only one surface coming into direct contact with the food substances, the entire film would be immersed in the relevant "simulant". For testing of low temperature food stuffs, the "Simulant" would be tested at a higher temperature, for instance 20C instead of 4C and so forth.
Finally, Surface Cleanliness
Uncoated blades can still present a health risk if the surface has failed to be cleaned properly. Such a surface can harbour human pathogenic bacteria, fungi (in rare cases- one needs to be immunosuppressed) and other disease causing micro organisms. This scenario is easy to avoid by simply keeping one's knives clean (and of course the region under the handle and handle itself.
Of course even if you are a user of a coated surface knife, then you should also endeavour to keep it clean to avoid any chance of an infection if you were to accidentally cut yourself.
Still unsure?
If you are still unsure about whether to use your coated knife with food then I would strongly recommend that any knife to which a coating process has been applied should be checked with manufacturer before assuming it is safe to be used with food items.
Remember that manufacturers knives may be coated in non edible machine oil and or gun/weapon oils to prevent corrosion during storage and shipping etc. These oils are not considered safe for use with cutting food items.
* I've already written about Cerakote coatings, this was back in 2017 with well over 3k views, nothing has changed to what I said back then.
