Chemical cleaning of exchangers, boilers - water side - what preparation?

I would like to know what preparations you use to clean exchangers and boilers on the heating water flow side.
To be precise, it is mainly about removing iron oxides that can effectively block the boiler's operation.
Cleaning with a cleaning pump. There are several preparations on the market, but which one is effective?
I am thinking about Kamix S + or RADINER Fi but nowhere have I found an opinion whether they are effective.


The floor has not been warm for 5 years. The heaters were warm, but not all.

Dry oxide deposit from the tube inside the boiler that was blocking the flow.

Do you have mixed metals in your installation? Copper Aluminum Steel? Have you been drained for 5 years?
Such things are caught by the strainer at the pump - you should check it there sometimes and if there is a tendency to collect dirt, check it more often.
Oh, on the return in the lowest part of the installation, I would also put a filter in your place.

The installation is not mine. I am servicing the boilers.
In the case of the above installation made of pex-al-pex pipes from a well-known manufacturer, steel plate radiators, a mesh filter is on the return and, as it turns out, unfortunately it does not fulfill its role. The installation is never emptied.
There are more and more such cases and most often they start from the 6th year of use.
I have fernox F5, DS40, sentinel x400 and x800 cleaning agents, but for cleaning the heat source itself (boiler) they are too weak.
The cost of buying Kamix S + or RADINER Fi is in the range of PLN 500-700. But it is not known what is the cleaning efficiency?

Kamix works only well on gray stone, not the black iron stone which usually kills the boiler exchangers, we rinse (descalant) in a liquid, but I don't remember it, after 20 minutes black water with pebbles in a good concentration takes great, which I will be able to do exactly find out after a long session and we tried a few means and the descalant turned out to be the best. After rinsing, add an ordinary washing machine softener to refill it perfectly hardness to 4-5 German degrees, less scale build-up, in new installations it is an absolute necessity.

https://www.leroymerlin.pl/hydraulika/uzdatwa...do-pralek-i-zmywarek-h-10-gw-3-4-60-l-min-sr- 68-mm-equation, p403248, l998.html