26. Supposed remedies: neutralisation, WD-40 and the “harmless” chromium(III)

“Neutralisation”

Several of the manufacturers named in this analysis recommend “neutralising” chromium(VI) residues and present this as a sufficient occupational safety and health measure. The term suggests that chromium(VI) can be rendered harmless. In fact, it is a redox reaction: a reducing agent converts chromium(VI) into chromium(III). This succeeds almost completely only under favourable conditions, i.e. with sufficient contact between reducing agent and chromate, sufficient quantity, moisture and exposure time. On porous insulation materials, in interfibre spaces, beneath deposits and on hot or dry surfaces, these conditions are rarely met in practice. [22, 25]

itself states that a component is no longer considered neutralised after renewed thermal stress (“If the component part is subjected to thermal stress again, it is no longer considered neutralized.”). The cause remains: as long as chromium, calcium or sodium, oxygen and temperature coincide, the chromate forms anew in the next operating cycle. [11, 22, 50]

Moreover, treating chromium(VI) with a reducing agent is itself a use within the meaning of Article 3 point 24 REACH (“treatment”). Whether it falls under the planned EU restriction will be decided by the final legal text. [59, 60]

The term is already factually wrong. Neutralisation in the chemical sense is the reaction of an acid with a base to form salt and water, that is, a shift in the pH value. Chromate is not an acid-base problem. The transition from chromium(VI) to chromium(III) is a redox reaction, which requires a suitable reducing agent, a suitable pH range, sufficient contact time and proof of effectiveness.

What the application looks like in practice is shown by the work instruction “Instructie voorkomen blootstelling aan Chroom(VI)” of Vattenfall Generation NL, first version of 18 February 2019, last updated in full on 29 April 2024. It describes the formation path correctly: calcium chromate forms when a chromium-containing base metal comes into contact with calcium and an oxidising agent at temperatures around or above 350 °C; as the calcium sources identified so far it names certain anti-seize pastes and calcium-bearing insulation material. For the treatment it provides two agents, the Siemens Umwandler Spray and a self-mixed ascorbic acid solution, both with a limited shelf life and a mixing date to be stated visibly, the powder two years, the wet solution one week. The surface is sprayed or moistened, the solution has to be sticky enough or kept permanently wet, because the conversion can take several minutes, after which it is cleaned with a cloth. [115]

Ascorbic acid is, unlike the penetrating oil treated further below, a genuine reducing agent. The objection is therefore directed not against the substance but against the conditions. The evidence of effectiveness for the reduction of chromium(VI) comes from liquid-liquid systems. What is involved here is a liquid-dry treatment of an open surface which, in the turbine and engine environment, regularly carries oil and grease residues. Complete conversion is not to be expected under these conditions, and for high temperature insulation no proof of effectiveness exists.

The check on success hangs entirely on the colorimetric rapid test, in the instruction the TK11 test kit from MATinspired. If it comes out negative, then according to the wording no further measures and no protective equipment are required. Every cleaning operation is to be concluded with a negative test, and tools and used full face masks likewise go back to the store after a negative test. The instruction regards air measurements as unnecessary as a rule. What significance such a test has is shown by the French field study: on the turbocharger the laboratory analysis detected 869 ng Cr(VI), while the colorimetric rapid test at the same place came out negative (Section 19). [115]

Under the same instruction the insulation mattresses are misted with ascorbic acid and then put back into service; remaining insulation material is misted and disposed of as industrial waste. With that the reaction partner returns to the hot component together with the material, and at the next start-up all the formation conditions are met once again. For asbestos there is no instruction to treat fibres and then refit the material. [115]

For GE hardware the ascorbic acid has been suspended following a letter from the manufacturer, on the ground that it adversely affects the microstructure of the material; cleaning with WD-40 is prescribed there instead. [115]

At the event “Chroom-6 verbindingen onder thermische isolatie” held by iTanks and the Chroom 6 Informatie Kennis Centrum on 6 November 2025, six suppliers appeared with pitches: Insulcon, Kavarmat, OOI, Ecopoint, Sherwin Williams and Econtras. Ecopoint presented the “Chrome-6 Neutralizer”, by its own description a solution of acids which reduces Cr(VI) to Cr(III), ready to use and with a shelf life of at least two years. The formation conditions are named correctly on the slide: chromium in the stainless steel, temperature above 250 °C, calcium-bearing insulation, alongside potassium, sodium or magnesium, together with moisture and condensation. [116]

The certificate which SEEF B.V. drew up in August 2025 on behalf of Eco-Point International BV for the Chrome-VI Neutralizer (PR269) is correct in its approach, because it claims no more than what was tested. The effectiveness applies, according to it, “mits deze verbindingen oplosbaar zijn in de neutralizer-oplossing”, that is, only in so far as the compounds are soluble in the solution. The product ages and loses effect, the treated surface is to be kept wet for at least 15 minutes and must be sufficiently cooled, and if the test remains positive afterwards the treatment was insufficient and has to be repeated. For the check the certificate records: “Een negatieve uitslag is echter niet betrouwbaar”, a negative swab result is not reliable; a reliable analysis is then recommended, SEEF TK01 or laboratory analysis. And further: “Het is echter geen garantie dat blootstelling volledig wordt voorkomen”, the product being “een hulpmiddel binnen een veiligheidsstrategie en geen oplossing die alle risico’s zelfstandig elimineert”. A document that discloses its own reach in this way is the standard against which what is made of it can be measured. [116]

The pitch slide reproduces four points: effective neutralisation, 15 minutes of contact time on a cooled substrate, significant reduction of the probability of exposure and an aid within a safety strategy. Not reproduced are the solubility condition, the ageing, the repetition if the test is positive and the sentence on the unreliability of the negative test result. The closing slide instead advertises with “Bewezen actieve RTU vloeistof” and “Meten is weten!”. Measurement thereby becomes the argument, while in the certificate it is the point at which a warning is given about the negative result. The product name “Neutralizer” carries the same misunderstanding in its title, because what is described is an acid solution that reduces. [116]

The work instruction of Vattenfall Generation NL is older than these documents. According to its own version history the ascorbic acid was added on 11 June 2019, the cleaning with WD-40 for GE hardware on 28 October 2022, and the last full update is dated 29 April 2024. It could not have known the certificate of August 2025 or the investigation of WD-40 of September 2026. What can be assessed is therefore not its creation but its continued existence. At the event of 6 November 2025, three months after the certificate, Econtras, an insulation contractor of Isolatiebedrijf C.J. van Waas BV, presented the same instruction unchanged under the heading “Reinigen met Ascorbinezuur”, including the statement that this is an ascorbic acid solution produced by Vattenfall itself, and including the sentence that no further measures are required if the test result is negative. [115, 116]

For the penetrating oil prescribed in the instruction, the same laboratory that certified the effectiveness of the Neutralizer subject to conditions has refuted any reducing effect: 96.8 per cent recovery with chromium(VI) already in solution, no dose-response relationship with complete extraction and 5.8 per cent recovery on the solid as a solubility artefact. The two findings do not contradict each other, they separate what is effective from what is not. In the work instruction both agents stand side by side as equivalent cleaning methods.

In this practice the release from protective measures hangs on a method whose negative result the testing laboratory declares in writing to be not reliable. This statement concerns the test method and not a single product. The French field study points in the same direction, with 869 ng Cr(VI) in the laboratory analysis on the turbocharger against a negative rapid test result at the same place (Section 19). A measure whose check on success can come out false negative does not satisfy the duty under section 7 paragraph 9 of the German Hazardous Substances Ordinance to verify effectiveness by suitable methods where no limit values exist. In practice it leads to protective equipment being taken off, tools and respiratory protection going back into the common stock and misted insulation material being refitted. For asbestos nobody would release a black area on the basis of a colour rapid test.

The certificate is the most precise document in this chain and the only one that names its own limits; no criticism attaches to the testing body in this, on the contrary, it set out the finding and its reach in full. What becomes of it in industrial circulation is something else: under well-known logos, correct certificates are cut down to four advertising points, the conditions fall away, and the lay reader is given the impression of safety where the certificate expressly gives none. The effect of the technical instructions of large groups of companies reaches furthest here, because they present the handling of a carcinogenic compound that is hazardous to water as a normal work step, with a spray bottle, a cloth, test strips and subsequent reuse of the material.

The German statutory accident insurance institution for the construction industry states on its page “Chrom(VI)-Verbindungen an Edelstahl” that “chromate-reducing fibre binders can be used”, and: “These reduce the chromate to uncritical chromium(III) compounds and bind fibres.” The only reservation that follows is that the use of a reducing agent may “where applicable have negative effects on the treated materials” and is to be agreed with the client. Proof of effectiveness, the presence of oils and greases and the duty under section 7 paragraph 9 of the German Hazardous Substances Ordinance to verify effectiveness by suitable methods where no limit values exist do not appear. The classification of the reaction product as uncritical moreover makes no reference to the findings treated further below: the sensitisation marking Sh which the MAK and BAT value list 2026 gives for the soluble chromium(III) compounds, the assessment by the French agency Anses of 2021 and the mobilisation of fibre-bound chromium(III) as chromium(VI) according to Walter et al. 2022. Elsewhere the same page records that the chemical formation mechanism is “at present not yet fully clarified”, and in the same text names the thermal insulation materials containing alkali and alkaline earth metals as a contributing factor. [117]

How an established reduction is organised is shown by cement. Entry 47 of Annex XVII of the REACH Regulation limits soluble chromium(VI) in cement to 0.0002 per cent, that is, 2 ppm of the dry mass. This is achieved by the addition of a reducing agent, predominantly iron(II) sulphate, stoichiometrically 3.22 mg Fe(II) per mg Cr(VI), in practice overdosed by a factor of eight to twenty, homogeneously mixed in, with a reaction that begins only with the mixing water, and tested in accordance with EN 196-10. The effect declines during storage; moisture and oxygen accelerate this. What is carried over from this is the spraying of a solution onto an oily surface in the engine room, without dosage control, without a standardised test method and with a rapid test as acceptance. [118, 119]

The operating instruction “Ausbau chromatbelasteter Dämmstoffe” under section 14 of the German Hazardous Substances Ordinance, available through the hazardous substances information system WINGIS of the German statutory accident insurance institution for the construction industry, classifies the activity with the sentence “These activities or processes are carcinogenic.”, carries the signal word Danger and records: “Chromium(VI) compounds can cause cancer!” It prescribes the demarcation of the work and remediation areas with a warning sign, low dust work procedures and equipment, work only with extraction, work with a fresh air supply, dust extractors and industrial vacuum cleaners of dust class H, continuous monitoring of function and extraction performance, covering with sheeting where cleaning facilities are lacking, cutting of the material exclusively with a knife, scissors or hand saw, immediate collection of the waste, separate changing rooms and a washroom with showers as a black and white facility, collection of the disposable protective suits at the end of the shift and the sentence “Do not reuse removed mineral wool products.” As personal protective equipment it requires close-fitting safety goggles for overhead work and heavy dust generation, protective gloves of chromate-free leather or nitrile-impregnated cotton gloves, a disposable protective suit type 5 and respiratory protection with the requirement “Always wear respiratory protection.”, implemented as a P3 particle filter on a half or quarter mask or as a particle-filtering half mask FFP3. In this list “Use chromate-reducing fibre binders.” stands in second place, between the zoning and the low dust work procedures. [126]

Compared with the German TRGS 561 the operating instruction goes further in several points. Section 5.9.3 paragraph 5 permits class FFP2 respiratory protection for short-term activities; the operating instruction has no short-term level and requires P3 or FFP3 throughout. Dust class H, the fresh air supply and the black and white facility are not named by the TRGS at this point. On eye protection the operating instruction falls below it, because the TRGS requires it without restriction, while the operating instruction ties it to overhead work and heavy dust generation. The chromate-reducing fibre binder does not appear anywhere in the TRGS 561; the terms fibre binder, binder and neutralisation are entirely absent there. [126, 19]

The publicly accessible information page of the same accident insurance institution carries not one point of this catalogue. It describes the formation path, names as contributing factors highly chromium-alloyed steels, oxygen, temperatures of about 350 to 800 °C and thermal insulation materials containing alkali or alkaline earth metals, identifies yellowish deposits consisting predominantly of calcium chromate as the most frequent finding, and offers the fibre binder as the only action, with the sentences that it reduces the chromate “to uncritical chromium(III) compounds” and binds fibres, and: “This lowers the exposure.” The only reservation that follows is the reference to possible negative effects on the treated materials and to agreement with the client. Respiratory protection, zoning, extraction, the black and white facility, the ban on reuse, the risk assessment, substitution and the TRGS 561 do not appear on the page. For the protective measures it refers to the lead German statutory accident insurance institution Energie Textil Elektro Medienerzeugnisse. [117, 126]

The same abridgement occurs on the industrial side, there with the same vocabulary. The German-language product page of Eco-Point International BV for the Chrome-6 Neutralizer describes the agent as an acid-based, biodegradable neutralising liquid “which converts harmful chromium-6 into harmless chromium-3”, and lists among the particular advantages: “Chromium-6 is converted into chromium-3, that is, from a carcinogenic substance into a harmless one.” The formulation “the harmless chromium-3” appears at two further places on the page. The page contains nothing on contact time, protective equipment, the risk assessment or disposal. The testing is referred to with the sentence that the Chrome-6 Neutralizer has been tested and certified by the independent laboratory SEEF; the conditions which that certificate expressly names do not appear there. The German statutory accident insurance institution for the construction industry with “uncritical chromium(III) compounds” and the supplier with “harmless chromium-3” thus make the same statement. The state of the findings on chromium(III) is set out in section 27, with the sensitisation marking Sh for the soluble chromium(III) compounds, the assessment by the French agency Anses of 2021 and the mobilisation of fibre-bound chromium(III) as chromium(VI) according to Walter et al. 2022. [127, 116]

As an assessment: in the public account a complete protective regime becomes a single measure, provided with a statement of effect that appears neither in the operating instruction nor in the TRGS 561 and for which no proof of effectiveness is required. A company looking for the duties that apply to it meets this account first, because it is the public entry point, while the operating instruction has to be called up in the hazardous substances information system. The question whether this abridgement was considered during drafting remains open. The effect occurs irrespective of that, and it reaches further than any manufacturer's statement, because it stands under the mark of a statutory accident insurance institution and is therefore citable.

A third supplier makes the same statement. The product page of MATinspired B.V. for the TK20 Chromium-6 Neutralizer describes the agent as one that “neutralizes and removes chromium-6 in surface contaminations on metals” and explains the effect by saying that the chromium(VI) present is “converted to non-toxic chromium-3”. There are thus three identical classifications of the reaction product: uncritical with the German statutory accident insurance institution for the construction industry, harmless with Eco-Point and non-toxic with MATinspired. [131]

The questions and answers of the same supplier name the limits that are missing from the product page. The agent has no effect against airborne particles, it presupposes cooled components, it is not intended for metal with gaps or bore holes, it is to act for at most about ten minutes and is then wiped off and rinsed with water. On the completeness of the conversion it says: “We cannot guarantee that the neutralizer liquid will remove/neutralizer all chromium-6.” On the durability of the result it says that re-formation has not been observed at room temperature, which means that the treated and refitted component at operating temperature is not covered. On protective equipment the answers name protective gloves and eye protection as the minimum, list P3 respiratory protection and protective clothing as a recommendation and close with the sentence: “It is the sole responsibility of the user which appropriate security measures should be used.” [132]

In both documents the proof of effect rests on the TK11 test kit of the same supplier. The same test kit is, in the work instruction of Vattenfall Generation NL, the criterion according to which protective equipment is taken off, tools are returned and misted insulation material is refitted. On this method the certificate of the testing body records that a negative result is not reliable, and the French field study shows the same finding with 869 ng chromium(VI) in the laboratory analysis on the turbocharger against a negative rapid test result at the same place (Section 19). [115, 116, 132]

As an assessment: an agent whose complete effect the manufacturer does not guarantee is accepted on the basis of a test whose negative result the independent laboratory declares to be not reliable, and the selection of the protective measures is passed to the user, while the German TRGS 561 lays them down for this application case in section 5.9.3 paragraph 5. The substitution of the material containing alkali and alkaline earth oxides, which would put an end to the renewed formation, does not appear in any of the manufacturer documents. [19]

WD-40

In practice, the penetrating oil WD-40 is in some cases regarded as a remedy against chromium(VI) and used during maintenance work. The origin of this practice can be named. The Safety Bulletin Summary of the British industry association Energy UK of September 2019 records that members have experience with the use of WD-40 or comparable agents and cloths “to immobilise and wipe away Cr(VI) residue”. What is described is the binding of dust before wiping, not a chemical conversion. The same document already names the three conditions of formation, a calcium-bearing product, temperatures above 300 °C and chromium-containing steel, and requires that presence be assumed at all power station sites. [92]

WD-40 has no reducing effect. SEEF B.V. tested this experimentally. With chromium(VI) already in solution the recovery after the addition of 2 ml WD-40 remained at 96.8 per cent, 240.7 against 248.7 µg/l. With a reference paint sample with complete digestion no dose dependence appeared; the values lay between 1,280.0 and 1,384.5 mg/kg against 1,265.0 mg/kg in the control and thus all above the control. According to the manufacturer's safety data sheet the product consists of 55 to 75 per cent by weight aliphatic hydrocarbons and base oil and contains no component with a reducing action. [91]

The third experiment explains why the measure nevertheless appears effective. Solid chromium(VI) in direct contact with WD-40 and then dissolved in water gave a recovery of 5.8 per cent, because the chromate clumped in the oil phase and remained withdrawn from the measurement. Whoever samples after an oil treatment measures a fraction of the chromate present. The finding confirms the measure, while the chromate remains unchanged on the component, in the cleaning material and in the waste (Section 17). [91]

The supposedly harmless chromium(III)

The reduced chromium(III) is frequently presented as an essential and natural trace element. In 2014, however, the European Food Safety Authority EFSA found no evidence of the essentiality of chromium(III) and considered the setting of an adequate intake to be inappropriate. [61]

Furthermore, the chrysotile study by Walter et al. (2022) shows that fibre-bound chromium(III) can be mobilised as chromium(VI) under oxidative conditions at physiological pH, which is taken up by lung and mesothelial cells. Industrial dusts can thus act as carriers through which supposedly harmless chromium(III) returns to a form that enters the cell. In the cell nucleus, it is then again chromium(III) that forms the DNA adducts. [4, 53]