hexavalent Chromium (Cr6)-compounds
(calcium chromate | sodium chromate | potassium chromate )
chromium (VI)-Compounds (calcium chromate) on calcium-containing high-temperature insulation
Insulating elements, insulating mattresses, insulating fabrics, insulating wool, fibers and mats
When dismantling insulating elements (e.g. as insulating mattresses, insulating pads, insulating pads, insulating mattresses or in other mat forms or as loose insulating materials), which are, among other things are used as turbine or engine insulation (gas turbine, steam turbine, diesel engine, gas engine and already on hydrogen engines), it cannot be ruled out to come in contact with calcium chromate, a Chromium (VI) compound, if the insulating elements and/or materials contain calcium or calcium oxides (chemical formula: Ca or CaO) and have been in contact with chromium-containing hot parts at operating temperatures of over 350°C (e.g B. stainless steel bodies such as manifolds, turbochargers, exhaust pipes, etc.).
More manifestations in their form than
sodium- orPotassium chromate (Na2CrO4or.K2CrO4)
cannot be excluded either.
if the insulating elements, materials and/or systems contain other alkali or alkaline earth metals such as e.g. B. sodium (Na) or potassium (K) or oxides thereof.
Immediate protective measures are required if yellowish dust is visible on the inside of the insulation or on the previously insulated component when removing the insulating elements. In this case, a chromium (VI) quick test must be carried out immediately. If this is positive (purple discoloration of the test stick), all measures must be taken immediately, e.g. in Germany from the so-called "Gefahrstoffverordnung" (GefStoffV) and the latest version of which you can download if you click here.
The carcinogenic chromium (VI) compound was blown out into the engine cabin due to a damaged insulating half-shell, and other chromates burned onto the line
Insulation pads containing calcium are still used; the calcium oxide in the insulation fabric reacts oxidatively with chromium alloys of the gas turbine and forms the carcinogenic chromium (VI) compound calcium chromate (CaCrO4)
the stainless steel wire reinforcement of the insulating fabric contains chromium, which highly oxidizes with the calcium oxide of the insulating fabric to form the hexavalent chromium compound calcium chromate
the calcium-containing insulating fabric of the second mat layer of a steam turbine of a German manufacturer reacts with the chromium compounds of the stainless steel fastening elements, also here high oxidation to calcium chromate
The calcium-containing inside of the insulation mattress (insulating fabric) and the stainless steel-containing pins of the turbine trace heating are sufficient to cause the chromium (VI) compound calcium chromate to be formed in relatively large quantities
American manufacturers in particular prefer stainless steel mesh as the outermost contact layer for high-temperature insulation. The wire mesh is in direct contact with calcium-containing fiber mats, high oxidation and the formation of an alkaline-earth chromium (VI) compound is preprogrammed.
lateral direct contact of the calcium-containing fiber mat with a chromium-containing engine hot part is almost a guarantee for the formation of calcium chromate (Cr6)
The extensively contaminated insulating element must be disposed of as hazardous waste subject to labeling. An engine cleaning is also pending.
Here, too, the chromium-containing stainless steel wire reinforcement reacts with the calcium-containing insulating fabric
also in this insulation of an austrian gas engine the calcium chromate formation is caused by the combination "chromium containing stainless steel with calcium containing thermal insulation".
as Chromium(VI) compounds subject to these chromates also the restrictions in Annex XVII, number 47 and 72 of the REACH regulation.
Hexavalent chromium compounds are toxic (due to their oxidizing power) as well as carcinogenic, especially when airborne and inhaled.
You can download a data sheet on the chemical properties and information on the dangers of calcium chromate for humans and the environment here.