Corrosion after 2 weeks??

[Natanael]

Drained the loop to modify the pump/res mounting and while removing some fittings i noticed the brown smudge or corrosion around a 90 degree fitting. I am using the Mayhem Pastel White premix and a copper water block that I designed and manufactured. The fittings that I'm using are all EK Black Nickel, couple with an EK Coolstream PE and a D5 pump which supposedly do not have any Aluminium parts. What could be the problem?

 

 

[Natanael]

1 minute ago, starcoaster said:

radiator? is that aluminium-free too?

As per EK's website the radiator has brass chambers, 90% copper tubing, copper fins and an aluminium housing.

[Natanael]

Just now, starcoaster said:

yikes okay. with that speed of corrosion it must be making contact with some somewhere. can you throw an inhibitor coil or some inhibitor solution in there for now?

Could it be that maybe the very diluted vinegar solution that I used before filling the Pastel might have affected the Pastel? I'm asking this because I did not flush the system again with pure distilled after the diluted vinegar.

[SolarNova]

You should always neutralize after a vinegar wash. Baking soda works.

[Natanael]

3 minutes ago, SolarNova said:

You should always neutralize after a vinegar wash. Baking soda works.

How do you recommend going about it? How much baking soda should I put with 1 litre of distilled water?

[SolarNova]

Only a small amount, maybe 1 teaspoon. Mix it well so its all dissolved, then flush the system. Once that's done rinse the loop again with just distilled, then your good to refill.

[ozchemist]

Upfront : I'm not a computer builder - I'm an industrial chemist. My interest is in coolants.

 

If you're suffering corrosion due to differential metals you need inhibitors that will work specifically with those metals. If there is aluminium in the loop you want 2-EHA sodium salt [sodium 2-ethylhexanoate]. If there's copper or brass in the loop you need sodium tolytriazole.

 

In bigger cooling systems which have differential metals (think Mack trucks / generators / etc) a typical formulation will have:

 

3 - 7% Sodium 2-EHA [Na 2EHA]

0.1 - 1% Sodium tolytriazole [NaTT]

1 - 2% 2-EH Imidazoline 

0.01 - 0.1% microbial inhibitor (usually CMIT/MIT - isothiazolone)

0.01% Dye (uranine or fluoresceine)

~90% Demineralised water or glycol/DI water mix (depending on fluid)

 

All of the above have a specific purpose :

 

Sodium 2-EHA is an aluminium and iron anticorrosive based on carboxylate absorption chemistry.

Sodium tolytriazole is a copper and yellow metal inhibitor based on triazole (amine) chemistry.

 

Both strongly absorb to their respective metals and inhibit ion solubilization into the carrier (water / glycol) - they ONLY absorb as a molecular monolayer, so heat transfer interference is minimal and there's plenty of residual material in the loop.

 

2-EH Imidazoline is present as a buffering agent to help keep pH around 9.0 - ideal for aluminium / iron anticorrosion.

 

CMIT/MIT inhibits microbial growth.

 

Dye for the pretties.

 

Water or glycol/water mix for heat transfer - you only need glycol if you're going above 100°C and at ambient pressure.

 

Some systems will include a surfactant (wetter) - typical choice would be an EO/PO block copolymer wetter (Teric 164 @ 0.1% or Dow Ecosurf LFE) - low/no foam without the use of an "antifoam" [usually a silicone that will foul the system].

 

This sort of system lasts for years (800,000 km) in big engines without showing any significant corrosion - the fallaway parameters are pH and NaTT concentration. pH must always be > 8.5.

 

In small systems, like computers, your exposed metal surface area to volume is probably higher - so work to the top of the range (5-7% Na 2-EHA, 0.5-1% NaTT), use a wetter - this should last the life of the computer without needing to be changed / replenished.

 

For those people who are saying to use "only" demineralised water - forget it. Demineralised water will happily corrode your systems - for a start, it has no buffering potential, so it will absorb gases from the air which will make it acidic and, hence, corrosive. Secondly, it quite nicely acts as a growth medium for all sorts of microbes - leading to Microbial Induced Corrosion (MIC). So, even with demineralised/deionised water you need a biocide, a buffer and a corrosion inhibitor.