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the chromate dilemma

Updated: Jul 30, 2021

Possible release of the hexavalent chromium compound calcium chromate when dismantling calcium-containing high-temperature insulation from CHP engines, turbines and exhaust pipes.




calciumfreie Isolierung Motoren
Positive "chromium (VI) rapid test" on an insulating fibre that had been in use

Calcium-free high-temperature insulation systems for your power generators


The Chromate Dilemma


“the insulation materials used so far for engines, power units contain calcium oxide (CaO). In combination with engine parts containing chromium and other stainless steel components, calcium chromates can be formed at higher temperatures, which can be released during maintenance work and pose a risk to health and the environment.."

Calcium chromate belongs to the carcinogenic and particularly environmentally hazardous chromium (VI) compounds, which can be found in many tables of banned or restricted substances (including REACH).


Chromates can be formed when, for example, chromium (III) compounds, components of most stainless steel alloys, "oxidise" at high temperatures with alkaline or alkaline metals (calcium, sodium, potassium, etc.) to form hexavalent chromium compounds.


Entstehung Calciumchromat calciumhaltige Isolierung
Calciumchromat Entstehung calciumhaltige Isolierung

The higher the chromium content of the stainless steels and the higher the CaO content of the insulating materials, the higher the probability and quantity of calcium chromate (CaCrO4) formation.


But other alkali and alkaline earth metals also lead to the combination of chromates, as can be seen in the graph below:




Calciumchromat, Natriumchromat, Isolierungen, Chrom (VI)-Verbindungen
Chrom (VI)-Entstehung (Chrom (VI)-Verbindungen) in Verbindung mit Calcium, Natrium und Kalium

Almost all commercially available insulation materials contain calcium oxide (CaO) in proportions of 15-40%, and/or sodium in proportions of 5% to 30%.


Thus, the above-mentioned "chromate dilemma" is unfortunately a reality, even if many companies do not yet sufficiently realise and evaluate this problem.


Any calcium-containing high-temperature insulation of bodies containing stainless steel, such as exhaust gas manifolds, turbochargers, piping or exhaust gas aftertreatment systems, is therefore a potential source of damage to health through skin contact or inhalation, or a danger to the environment, which can be read about at "pubchem", among other places:





Sicherheit und Gefahren Calciumchromat
Sicherheit und Gefahren Calciumchromat

The formation of the carcinogenic and environmentally harmful chromium (VI) compound calcium chromate (CaCrO4) in connection with calcium-containing insulation is not only theoretically possible, it is also shown in so-called "chromium (VI) quick tests" carried out on dismantled insulation elements:



Chrom (VI) Nachweis Calciumchromat Isoliermatte
Calciumchromat (Chrom (VI)-Verbindung) an der Innenseite eines Isolierelements



Chrom (VI)-Nachweis (Calciumchromat) Isolierung
Chrom (VI)-Schnelltest thermische Isolierungen


Chrom (VI) haltige Glasfasernadelmatte (Calciumchromat; Chrom (VI)-Verbindung
positiver Chrom (VI) Schnelltest (Calciumchromat) Glasfasernadelmatte


The health of the people who may come into contact with our insulation products is close to our hearts!


The preservation of our environment and the natural protection of our drinking water are equally important to us!




If insulating materials containing calcium can lead to the formation of carcinogenic and environmentally harmful substances in the high-temperature range, then the use of insulating materials containing calcium is not an option for us and the use of calcium-free materials is without alternative.


For this reason, all Kavarmat products and systems are manufactured exclusively from calcium-free and sodium-free materials!


No calcium - no calcium chromate

No sodium - no sodium chromate



Safety for people, machine and environment



Thank you for your attention and look forward to our next article: "Taking back used insulation elements when ordering new calcium-free Kavarmat insulation".



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