Remember when EK had the nickle flaking off their blocks years ago and blamed it on the liquids? Or maybe you weren't watercooling yet.
They retracted their statement and had a massive recall due to poor plating on the blocks.
They want you to buy their liquid. They want to ensure they have no issues.
Yes they did go through that period where they had plating issues - however that was sorted some time back although probably not handled as best as could have been. Their recent offering have been fine as far as I know.
There is NO corrosion in a loop with the proper metals.
The crux of the issue is that we cannot guarantee what metals are used in our loops. Take our rads for instance - Most people think the better units are all copper. In reality they consist of copper plus many other metals which form the various solder alloys utilised by various manufacturers - all possible points where corrosion can take hold.
There are too many unexplained cases of corrosion on the various forums where people have utilised just straight distilled and a kill coil so I'm not convinced that running just distilled will work for all the various combinations of all the hardware out there.
While distilled water causes no corrosion, this is only the case while it has not absorbed ions. Over time it absorbs ions from the metals and only in a few days it will become conductive allowing corrosion to form. The speed of corrosion is what we basically control by selecting the appropriate materials that make up our loops to effectively slow down the corrosion.
To be fair to the EK staff member replying to the particular thread he did not really push their product but did highlight that their product was based on glycol and the main advantage of a glycol based solution over just straight distilled etc.
Over the years I myself have run automotive glycol solutions with excellent results. One example I like to refer to is where people may use straight distilled with copper blocks.
If you run straight distilled, the copper will always tarnish relatively quickly and end up black - While this is not really a major issue for us, what it does show is that oxidisation has formed ie very light corrosion is taking place. If you run a glycol based auto coolant then the block will stay shiny even a year later showing that the surface has not oxidised - simply due to the corrosion blockers in this type of fluid.