Coolants & corrosion

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alan s
RIP 2010
Posts: 2542
Joined: 26 Jan 2001, 15:53
Location: Australia
My Cars:
x 6

Coolants & corrosion

Post by alan s »

We often get requests on the forums for advice relating to why certain cars radiators or the heater matrix seems to be continuosly rotting holes in themselves.
It has been blamed on the salted roads in winter causing corrosion from the outside in and in some cases this is possibly a reasonable explanation, however, even that problem can be overcome to a degree.
I have to ive with a different set of circumstances, but there is a parrallel in some respects. We don't get the salty snowy roads, just the opposite, but the air in these coastal towns is so salty I've seen gutters rusted off houses and cars left outside turn to piles of red dust real quick, so we also have problems with both internal & external corrosion also.
If I have cause to remove my radiator on any of my cars for any reason, I always keep a couple of cans of cheapy aerosol spray enamel on hand and blast a coat all over them before I refit to the car. It makes the car look a bit swish when you see a nice shiny black radiator through the grille or when you look under the bonnet as well as giving it some protection from the harsh salty/sandy air.
As far as internal corrosion goes, in most cases there is a cause that has been overlooked.
Most if not all car makers include somewhere in their manuals a recommended coolant mix (ie) 50% glycol to 50% water (as an example) but most owners will go to the local auto store & buy a premix special with no idea or interest in what the make up of the premix is. Often in cases of "no brand" or unknown stuff, the mix can & often is as low as 10% coolant - 90% water so it's not giving real good protection. If this is then topped up om occasions, using plain water, it's only a matter of time before the mix is negligable amount of coolant to 99%+ water. This is bad enough, but if tap water has been used, this is often acidic in structure and when this is added to the mix of various metals in the modern engine, then this is where the electrolysis begins to eat away at all the internal parts. Naturally, the parts making the easiest targets are the thin walled particularly aluminium or alu based alloys such as radiator cores and heater matrix.
If you must buy a pre-mix, check it's consistency on the label before you purchase & see if it is up to manufacturers specs. From memory, on a BX 16V, with all alloy motor, the mix is 50/50.
When using a concentrate, firstly check the type. There are two types normally available, Glycol or OAT.
Glycol has been bagged for years, unjustly in my opinion whilst OAT its competitor I have found can tend to slime up the cooling system. Either way the most important thing isto be sure you use a demineralised water. Some people even catch their own rainwater in plastic so as to have some on hand. This is OK providing there are no industrial pollutants in the rain water.
Presently I'm running a "95% Coolspec Glycol" at a 50/50 rate in my 16V. I top up when necessary with demineralised water and as I bought the Glycol in a 5 litre bottle, I occasionally top up with the Glycol to try & maintain the consistency.
It's often said that coolants topped up with water go acidic; that is true, they do but there's nothing mystical about this. The acid is added as soon as you put tap water in your cooling system.
Hope that explains it all.
Alan S
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