Coolant advice needed

[Bruce Caulley]

Morning all,

 

We are having a problem with corrosion on our 7075 aluminium components. I am leaning towards galvanic corrosion as the culprit, but putting zinc annodes on the fixtures and on the sub plates isn't working. Parts come off the fixture with black splotches after only a few minutes of machining. We are using Hocut 795B but we also have a large coolant recycling tank out the back that oilskims and removes fines. The recycled coolant seems to promote this corrosion more than fresh made. My theory is that it is dissolved metals in the coolant itself and that we either need to add a different filtration/processing operation to the recycled coolant before re-use OR use a different coolant altogether. One that won't promote galvanic corrosion.

 

What coolants are others using? Most of our work is ally aircraft components, but we do a mix of steels and exotics also. Some of the coolant I see in machine demonstrations is clear or almost so. What is this stuff?

 

Any comments or suggestions appreciated.

 

Bruce

[Guest]

Bruce,

 

We use Blasocut 2000 CFSW

 

Blaser Swisslube

 

We've been happy with it.

[Greg Williams]

Bruce,

 

In have had good success with this

 

Coolant

 

Stabilo range

[J Coulston]

Blasocut 2000 Universal

[DavidB]

Bruce we use Hocut 795 here too with no problems.

Houghton come in once a month and analyze the coolant in each machine they check PH levels Bacteria and concentration. Concentration they recomend 4-6% and Ph of 8.5-9.5

 

HTH

[Bruce Caulley]

David,

Do you have a recycling system? The coolant works great until it has been "cleaned" and re-used. Houghton are in regularly to check the usual levels you mentioned, but I reckon if they were monitoring dissolved metal content/conductivity it would be off the dial.

 

I set up a small experiment with a battery and a couple of bits of scrap 7075. The new coolant had a couple of bubbles appear around the annode, but the old coolant looked like it was boiling.

 

Bruce

 

Bruce

[DavidB]

quote:

---

David,

Do you have a recycling system?

---

No each machine has its own coolant supply.

We completly claen out the coolant each Xmas.Other than that its just maintained by they operators.

[Steve at JPI]

I've always liked Trim. I thought Blaso was a lot of hype and not a lot of performance for the price. The "natural" vegetable based Blaso smelled like popcorn when it smoked on heavy cuts. Just my 2 cents.

[Chris Rizzo]

I know exactly what your talking about Bruce. I've experienced the exact same type of corrosion, usual occurs in a day or so...but not hours. Stacking 7075 parts directly against each other will cause it too, so it certainly sounds like galvanic action in your case. We use Blaser 4000 strong, which is a little overkill for aluminum, but not a problem. It doesn't gall with surface toolpaths, and cleans/decants nicely. We change/clean/decant it every third month or so. No inline filters either.

 

hth

[Brian Scullion]

We don't use coolant but an aerosol mist directed through the cutting tool (basically veg. oil)instead you can see exactly what you are cutting at all times

We cut 7075 aircraft structure components only

on a large 30,000 rev's high speed 6-axis milling machine.

 

We would never go back to coolant again it's just to messy.

[Bruce Caulley]

We had one part corrode in a few minutes! The conductivity in that coolant must be through the roof. We are having chemical analysis done now to try and pinpoint the root cause so we can put it to bed.

 

I like your vege oil method Brian. I'll look into it.

 

Bruce