Coolant, rust, foam, and DI water

[swarf_rat]

I have had a bit of a foaming issue with coolant, and now I am seeing some rust. This is happening under the vise, inbetween things, places that don't dry out for a very long time. It doesn't seem to happen on any surfaces that dry.

Some people have recommended DI water in the coolant mix. I have used well water, it is treated to remove iron and maganese through a improved green sand filter. The cheap test strips put it at about 120 - 150 ppm total hardness. I don't have a TDS meter. The reading I have done suggests that DI water is actually somewhat more corrosive than hard water. But also that the hard water may bind up the anti-corrosive additives in the coolant, so maybe DI water is better. I get quite a bit of evaporation between uses, mill will go several weeks not being used, then I have to top up the tank with 10 or 15 gallons of fresh mix. I test the concentration and keep it at the high range - about 10%. But if I am adding that much water lost through evaporation, surely I am increasing the hardness over time too.

A DI filter will cost a few hundred, not the end of the world but money I would rather spend on beer if the DI doesn't do any good. So:

Who has experience going from tap or well water to DI water, all other things being the same? What was the result? Improvement or no, dramatic or marginal?

 

[adama]

De ionising water for making coolant would be kinda pointless. Naturally water likes to have a minimum dissolved solids of something like 50ppm. Try taking it below that and it will actually work pretty hard corroding stuff to get back there. That said its anyone's guess once its mixed with coolant what it would register as with a TDS meter, no doubt highly dependant on the exact coolant.

That said i make up what little coolant i need with reverse osmosis water, mine has a TDS of about 30 on a good day, it does seam to mix a bit nicer, but i don't use flood coolant enough to really comment on corrosion issues. All i can add if you have a 150ppm of hardness you can probably double that to get a ruff tds, hence your probably looking some were around 300ppm Ie 0.3% of your coolant is dissolved solids from day one. Evaporation won't deplete it and every time you top it up your increasing it. But that said theres also carry over and some of the disolved solids will get displaced with other things. Hence in a years time assuming you have probably totally topped it up in volume three or four times over your going to have a lot of other crap in there. How much would need testing to know. Using purer water your adding less hardness and IMHO its probably the calcium hardness that makes the coolant unstable and increases the foam issues + uses up the buffering agents in good coolant.

Personally i would stop at a reverse osmosis filter setup, its cheap to run, di has some not insignificant resin costs. Great if you need that quality but expensive if less will do. DI filtration is normally a post reverse osmosis filter step anyhow unless you have really pure well water to start with (like low TDS). other wise your using the di filter bed to remove the massive qty of hardness and such which will soon deplete it.

 

[swarf_rat]

Wonder if TDS in coolant can be measured with a standard cheap TDS meter? These are resistance based, no?

What you wrote kind of reinforces what I have read elsewhere. An RO setup costs a bit more than a DI filter, I only need probably 200 gallons a year out of it, so the media is not an overriding cost issue. More of concern would be the maintenance required of it in very intermittent use. I understand that if I dry the DI resin I can store it for a couple months and use it again. Drying it in these filter cartridges would be easy. RO I'm not so sure - I have an RO plant on the boat and it is by far the most maintenance intensive piece of equipment installed there. Has to be used all the time, has to be cleaned and flushed all the time.

My coolant is about a year old now, I have added at least 100% makeup from evaporation. There isn't very much carryover - not that much use and a pretty efficient Knoll drag conveyor - I probably loose more from skim vacuuming. So whatever my TDS was, it is probably double that now. That seemed like one advantage of using DI water - it wouldn't change much over time.

I have been dealing with the foaming using an anti-foam agent, which works for a while and then needs to be replenished. But the rust is not something I want to live with.

 

[PixMan]

When you mix your coolant for replenishing the tank, how exactly do you do it? If you add water to the concentrate, the coolant may test OK at that time but soon seperate again at some level. That could cause rust as the concentrate isn't stable in the mix as a thin flim in the places described.

Always mix concentrate into the water, using the mantra "Oil-In-Last" or simply, "OIL".

Of course if you are mixing it the right way, something else is going on to allow rust to start because as far as I know all metal-cutting fluids have anit-rust additives.

 

[swarf_rat]

I mix the replenishing coolant using a siphon mixer into a 5 gallon bucket. I don't see any evidence of the oil falling out of emulsion. Could be the anti rust additives are just getting used up after nearly a year?

I found some old threads addressing this topic (though not by using the search facility here which is useless...) and there are a few people advocating DI or RO water and claiming to see an improvement in coolant life, some questioning the cost of doing so, some seeing more foaming with DI water, but no one seeing MORE rust with DI water vs. tap water (though some postulate that they might expect more).

The problem areas I am seeing are thin spaces between iron parts like between the vise and the table, or the vise jaws and the body. These stay wet basically forever. Surfaces of the same bits exposed to the air aren't a problem. I have read that iron against iron can be fairly galvanically active, DI water might help here?

 

[Lost in LA]

Swarf

It you just want to solve the foaming problem go to Home Depot or equivalent and buy their spa anti-foam.

The soluble oil I use to buy (traditional type) seems to be poorer quality in the last few years. Goes sour faster.

I tried a few new ones and found Trim e850. It is a lot more expensive but has not gone sour in 6 months. No rusting parts. Smell is ok. Call up a local distributor and they will give you a sample. ( they gave me 5 gal for testing)

I buy mine from zoro
Metalworking Fluids E850 by TRIM - Cutting and Grinding Fluids by Zoro Tools Industrial Supplies

Lost

 

[Edster]

It's probable that the anti rust additives are being used up. That's the reason most all coolant mfgs recommend adding a 1-2% minimum makup solution.

I use DI water that I make from well water, works great.

I use cheap strips from mcmaster to measure the hardness.

 

[oldbrock]

Used to have that problem with rust under the vise or dividing head so always remove them from the table when cleaning up. I may leave the vise on if no coolant has been used but any time coolant is used the table is cleared and wiped down. Peter

 

[swarf_rat]

I have been using about a 2% makeup solution, I've never dumped just water in. But I guess I could still be using up the anti rust additives faster than they are going in, especially if there is any truth the the idea that the hard water binds some of it up.

I used to clear the vise off the table at the end of the day. But I have found these fancy new Orange vises can clamp most everything I do, so I am leaving them on more. And there are two of them. And I need to indicate them in to about 0.0001 all directions. So I've been lazy and left them.

I suppose some other coolant might do better, but let's stick to the question: given a certain coolant, is it better to use DI or tap water? Otherwise there are too many variables to contemplate.

 

[Homer]

For what its worth, the first machine I bought, I tried ever coolant known to man. The best coolant I found and have stuck with 100% satisfied is Etna Masterall syn 40. A clear synthetic coolant, no nasty smell, no paint loss, no rust (mix at 4%), expensive but well worth it for me.

 

[D. Valiket]

I have had a bit of a foaming issue with coolant, and now I am seeing some rust. This is happening under the vise, inbetween things, places that don't dry out for a very long time. It doesn't seem to happen on any surfaces that dry.

Some people have recommended DI water in the coolant mix. I have used well water, it is treated to remove iron and maganese through a improved green sand filter. The cheap test strips put it at about 120 - 150 ppm total hardness. I don't have a TDS meter. The reading I have done suggests that DI water is actually somewhat more corrosive than hard water. But also that the hard water may bind up the anti-corrosive additives in the coolant, so maybe DI water is better. I get quite a bit of evaporation between uses, mill will go several weeks not being used, then I have to top up the tank with 10 or 15 gallons of fresh mix. I test the concentration and keep it at the high range - about 10%. But if I am adding that much water lost through evaporation, surely I am increasing the hardness over time too.

A DI filter will cost a few hundred, not the end of the world but money I would rather spend on beer if the DI doesn't do any good. So:

Who has experience going from tap or well water to DI water, all other things being the same? What was the result? Improvement or no, dramatic or marginal?

Have your coolant rep send a sample of your water to the manufacturer of the coolant. They should check it and offer a recommendation. No cost to you.

 

[adama]

Firstly a non marine RO is a lot less maintenance. Mine is little more than a std house hold one, 10 micron sediment prefilter, carbon filter then ro membrane. I need the RO water for one of my customers (selling filtered water is damn profitable :-) and i only charge him what he use to pay as a delivery charge) I use - make about 50 litres a month. Same filters - ro is going on a year and still hitting the same TDS. Normally on start up i need to lob the first liter or so as it's tds seams always that bit higher. System simply stays wet - full of water all the time, just input and output valves closed, ro membranes must not dry out!

There is some pretty simple sums on-line that let you estimate DI resin life based on input water hardness (di resin will only absorb so much TDS). Based on my needs + input water TDS it was a far more expensive option after a year or 2. Equally you need to match the resin to the input water impurities to get the best results + longest resin life. Theres 2 diffrent types of di resin which collect diffrent impurities and there mixed to catch the lot, if the mix ratio does not match your input your going to get a even shorter resin life.

That said if you have a boat system why not just try the water off that for a few months and see if it helps?

 

[swarf_rat]

I have looked at the cheap RO filters, they have a couple of disadvantages for me: the flow rate for the inexpensive ones is very low, so filling a 100 gallon tank would take days or even weeks. The membranes are also sensitive to chlorine and I chlorinate the water as part of the potassium permanganate filtration system to remove the iron and manganese. If I take the water prior to the filtration system the RO system will quickly clog with biofilm from the iron bacteria. These are the things painting me into the DI filter box.

The boat is currently in the Chesapeake and I am in California, so it would require about a 3000 mile hose to try that....

 

[adama]

Slow delivery of the cheap ro is not a issue, its not like you really have to do anything till the tank is nearing full! (you fill a tank with ro warter, you don't use ro water like a hose pipe!) Due to the pressures i run at mine would take sub 3 days to fill a hundred gallon tank, its a 50 gallon a day membrane, but real life output is nearer 40 a day. As to the chlorine, IMHO if your treating at the correct rates then there should be very little make it past your green sand filter (it should be used oxidizing the iron any more than a left over trace and its bad news for your plumbing + health). Equally what little does the carbon filters can deal with assuming chlorine at normal mains supply levels Its why there there!

Di won't work in high chlorine either, first it will deplete all the sooner, secound chlorine will break down the resin into gue.

IMHO if chlorine is noticeable coming out of your tap it could be the biggest part of your corrosion and coolant issues. You realy should not have but trace amounts left after it has oxidized the iron out of solution. If chlorine is in the water then its going to be a big issue in the coolant probably a lot more of a problem chmistry wise than any hardness.

 

[swarf_rat]

I try to treat with 0 to 1 ppm free chlorine post green sand filter. But sometimes it gets up to 1 to 2. I don't know how sensitive the RO membranes are, only that the operating instruction for the boat unit say NO chlorine. It operates at about 1000 psi, maybe that makes a difference?

The cheap RO filters here are more like 10 - 15 gallons per day. Of course pressure dependent, I have only about 60 psi to work with, they are usually rated at 100 psi.

 

[adama]

Cheap ro filter of ebay was my source. I cheated and pretty much built my own unit up, Had some good but old - spare 10" filter holders off a old machine, just bought the sediment filer (£2 ish) and a carbon block pre filter (£8-9 ish) + new sealing O rings then got a RO housing + membrane + output flow restrict-or + plumbing bits of the bay (about £35 if i remember right). Your right the membranes are rated at 100Psi, but i only run mine at circa 35psi as that's all i get of the low voltage well pump i use (my well water has about half the TDS of mains) A RO filter setup will commanly get you a 20:1 improvment on impurities.

The carbon block pre filter is std to remove anything like your chlorine that will harm the RO membrane. Its recommended to protect the Ro membrane and remove chlorine when a ro set-up is used on a mains supply, which can be anything up to about your 1ppm of chlorine here, think you should replace it about every 6 months. I use it as my well possibly has traces of stuff that i can't detect but would screw with the chemistry of what the water gets used for. Hence so long as you use one your chlorine never gets to your ro membrane.

That chlorine could be a big part of your corrosion problems. Chlorine ions can affectively sit on a iron surface and act as a catalyst for rust with out getting converted into something else in the process (they help the oxygen combine with the iron). Hence your gradually increasing the qty of chlorine in your machine every time you top up. Heck you might almost be better off with your unfiltered well water, Iron reducing bacteria + the hydrogen sulphide they give off would potentially have a lot less affect on coolant + your hardness would buffer any acidity change from the sulphide produced by the bugs.

 

[IAMATT]

If your foaming and you have rust you could have one of these possibilities

1. Your mix ratio is too low (obvious with foaming)
2. Your contaminated coolant has failed
3. The water you mix your coolant with has a mineral that is neutralizing the O2 barrier in the coolant

 

[swarf_rat]

My mix ratio is at the high side of recommended at about 1:10. I know this by refractometer readings and having directly measured what is going in - all mixed in 5 gallon lots. So it isn't that, but could be #2 or 3.

I have a large carbon filter in the filtration system (by large I mean 5 feet tall and 16" diameter) which I have never turned on. Sounds like maybe I should try that first. It would remove the residual chlorine and maybe some other things in there. I hadn't turned in on because the water seemed fine (to drink) without it. But I do notice hard deposits where the water dries repeatedly.

But I thought chlorine was a dissolved gas, and dissipated quickly in still water exposed to air. That's what the aquarium people tell you - let it stand for a day or so and the chlorine will be gone and not kill the fish. There shouldn't be any in my tank after several months. Not true?

 

[adama]

What are you adding as chlorine before the greensand filter? If chlorine gas (what they use in the mains i belive as like this it treats any air spaces in the pipes?) Then the gas will dissipate. If its a chlorine compound it will take time to break down but could well end up trapped in the oil emulsion or as some other chlorine salt like compound. Ie seeing as you have hard water possibly some will end up breaking some of the carbonates down into calcium chloride, and thats a salt that loves to rust things better than normal salts of the sodium varieties.

As soon as you start adding more things chemistry and what happens gets complex quick. The advise of getting a sample tested from your coolant supplier may well be the right thing to do. Equally go careful messing with your water supply, a used but then isolated carbon filter could have anything growing in it a few years later when it is reconnected!

At 1:10 you mix ratio might simply be to high too, might do better dropping it back to nearer 8%

Back to the DI thing, you do realise with DI the resin is a use once then replace, not a simple back flush with water like a green sand filter. Hence its high running costs in replacement resin. I have no idea about carbon filters at the sizes your is, but again, back flushing is not really going to do that well at cleaning activated carbon.

 

[swarf_rat]

The chlorinating agent is Clorox, or sodium hypochlorite, delivered by a ratio metering pump from a diluted mixture. The water was intensively analyzed some time ago, I could look up the results but I am not sure what I am looking for. There was nothing remarkable in the results except iron and manganese, where were around .8 and .5 ppm if memory serves. After the chlorination and green sand filter, the results for both were None Detected.

I know the resin in the DI filter gets used up, but it looks like I would only need $90 worth a year to make what I need. The carbon filter does get blackflushed, claimed to last several years (7 - 10 was mentioned) in supplying household needs. And it can be emptied and rebedded with new material.

Why would too high a ratio promote corrosion? Seems like more is better in this case....