Rust inhibitor in plasma tanks

Starting a new topic for this, so I won’t be hijacking someone else’s thread… Not sure if people have discussed this much here…

Water is a poor conductor.

@subnoize , Rust inhibitor is used liberally in the water tank here, so the “water” is highly conductive. :smiley:

The plasma cutter is in use almost every weekend and often a night during the work-week as well, so the water table doesn’t get drained here. The rust inhibitor keeps the slats from rusting up, as well as all the tiny tiny dross in-between major cleanings. It is also nice to pull a piece of clean mild steel of the table and know it isn’t going to flash rust over-night. Here in the PNW those days are few and far inbetween, but in years past I’ve had those problems near the end of summer and the rust inhibitor has cut that right out. :slight_smile:

qd40_136_004058

I can’t remember if there has been a discussion of rust inhibitors for water tables here…? I use food grade sodium nitrite. Super cheap for a 5lb bucket.

Are others out there using something else?

Sodium Nitrite only works when you don’t have an aluminum tank. The one I was shipped is aluminum.

For those of us with aluminum tanks, do not use sodium Nitrate as it will seriously pit and degrade the aluminum. The weld will also embrittle and may crack over time.

https://www.publish.csiro.au/ch/pdf/ch9800169

In coolant systems where Sodium Nitrite is used will commonly interface with alumium components and we discovered the alumium will pit, embrittle and eventually fail.

It’s not “right away” but drain your tank, don’t let it sit. Rinse the tanks after use. The electrical fields developed in the tanks for Plasma machines enhance the effect so be adivised.

@subnoize ,Thanks for the tip. Some further research tells me I’m in for a catastrophic failure on the water table soon. (or two years ago and I still haven’t noticed) :wink: I’ve been using much higher concentrations (and repeatedly refreshing it) for the past several years (higher than those mentioned in Google & Wikipedia. I almost wonder if the deposition layer of steel / dross that has been deposited
and then passivated on top of the aluminum is protecting it below the water line.

Three summers ago and again last summer I had pulled the water table off the machine and had it out on the the back lawn to do a heavy manual scrubbing with a steel wire bristle brush. There is some sort of dark purple/brown/black amalgamated “alloy” for lack of a better descriptioncovering the walls and floor of the tank that elbow grease and a steel bristle brush would not clean up in ~2hrs of work. I wasn’t as interested in scraping through it as I was in cleaning out any spots of semi-permenantly attached dross.

From reading further on Google, looks like I’ll either be calling AVID to buy a new tank shortly or welding one up myself from sheet stock in an alternate material.

Well, AvidCNC should post care instructions for their tanks. They need to now as they have a customer who has been effected.

The only reason I knew about it was because of water cooled aircraft engines back in the 80s started having troubles as owners started using cheaper automotive antifreeze. One of those word of mouth things that ruined many engines.

There are several formulas for anti-rust, anti-dross and anti-splatter that are aluminum safe. They are very expensive.

If you remember back I was babbling about adding a 3,000 GPH recirculating pump and secondary storage tanks to my table, this very topic is what was driving all that.

I am sorry I didn’t mention this earlier :frowning:

WELL that explains all my leaks and the horrible pitting i have, bought my table used and was told by the seller to use this same stuff. now 3 years later (from new) and my water table leaks and is pitted really bad.

@support , It seems like CNCRouterParts/AVIDcnc needs to up there game here and put some direction in documentation. I suspect where we have gone wrong is A) the lack of direction, and B) information on the internet that does not specify the special case that AVID has which is an aluminum tank. I’m not looking forward to buying a new water table.

Yep, this is widely documented by all of the other plasma table OEM. It is surprising that AvidCNC doesn’t have this boldly printed and stuck on their tanks.

And, … just a few months on from this discussion…

How long does it take for neutral food safe sodium nitrate, that has been being used to preserve meats for a few hundred years of human history, to eat through an AVID cnc plasma water tank you ask? Yup, @subnoize call that one, it is going to happen. The answer here is just a hair under 4yrs. I was able to track through dates on photos, that I started using this in the tank in the first 1/2 of Jan-2020 and here this week I have two pin-hole leaks in the AVIDcnc water tank just a month shy of 4years later. @Eric AVID really needs two things added to their documentation. 1) a recommendation not to use this stuff (which is commonly used in industry for systems with steel water tanks). And 2) a recommendation as to what kinds of rust inhibitors people should use with all that exposed steel in the AVID cnc tanks combined with their aluminum shells.

-Kenneth

I’ll look into it. Personally I use straight water but I drain it afterwards. I have a really small table and I don’t cut all that often.

At HQ I believe they use Green Cut or something similar.

There’s some good information here I found: WATER TREATMENT

@da-kengineer-meister I think I would be calling and demanding to speak with management.

Even if this was widely known (which it isn’t) they should still put a big ugly red warning sticker on their tanks.

We all laugh about the warning labels on common household products but you just discovered how badly it can wreck your investment because somebody didn’t have enough forethought for a far less silly warning label.

These are our 4 recommended plasma additives/cooling liquids:

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