stainless steel and ozonation
stainless steel and ozonation
(OP)
I need a little help in determining what I need to ask to determine the nature of a problem one of my customer's is having.
We have a piece 316 stainless tube for a valve stem which passes through a 304 stainless guide, and has a plastic cap on one end.
As a method of cleaning, the customer uses ozonation(sp?).
The problem is that anywhere there is any type of mechanical contact, there appears to be some scoring of the parts, as well as a yellowish discoloration, almost as if the parts are being heated.
Since the product is drinking water, there can be no other lubrication than the product itself.
Is anyone familiar with the ozonation process? is there some kind of particulate which is created with either 304, or 316?
We have a piece 316 stainless tube for a valve stem which passes through a 304 stainless guide, and has a plastic cap on one end.
As a method of cleaning, the customer uses ozonation(sp?).
The problem is that anywhere there is any type of mechanical contact, there appears to be some scoring of the parts, as well as a yellowish discoloration, almost as if the parts are being heated.
Since the product is drinking water, there can be no other lubrication than the product itself.
Is anyone familiar with the ozonation process? is there some kind of particulate which is created with either 304, or 316?





RE: stainless steel and ozonation
The yellow discoloration you associate with the ozone treatment sounds like it's producing an oxidation. Stainless usually discolors to a yellow oxide around 600F. Maybe with ozone that occurs at a lower temperature.
RE: stainless steel and ozonation
Do either of you (or anyone else) know whether 316 would be more/less resistant to this oxidation or just the same?
Thanks for any tips in advance.
RE: stainless steel and ozonation
It may do worse since it has less chromium.
To minimize this condition you would need a more oxidation resistant grade, which is not necessarily the same as a more corrosion resistant grade. 302B, 309, or 310 would work if you can obtain these less frequently used alloys.
They are used for heating elements, furnace parts, etc.
RE: stainless steel and ozonation
I have also found that the oxidation products are quite tenatious. Cleaning the metal completely is difficult, and oils and common solvents don't really help.
My searches indicate that some sort of acid might be helpful, but I'd rather not use acids. I don't suppose you know of any surfactants/detergents that might help separate the oxide from the metal?
It's a long-shot!!
Cheers.
RE: stainless steel and ozonation
as far as detergents, etc. I haven't heard of anything.
Is your part something which can be hit with a fine wire brush? That might help clean it off, mechanically, but you'd probably have to passivate after that.
RE: stainless steel and ozonation
The methods to remove heat tint on stainless are given in the FAQ's at http://www.stainlesscenter.com. You need to register there, but it's free. Look under "clean stainless" and then "weld". The appropriate entry is about heat tint. There are several methods, using mechanical methods, phosphoric acid, or electrolytic.
The condition is similar to that encountered after welding when the heat affected zone gets various levels of heat tint that must be removed to restore corrosion resistance.
Since the problem is galling, I would recommend the abrasive methods since it will result in a superficial surface hardening. I have seen this improve galling resistance.
RE: stainless steel and ozonation
RE: stainless steel and ozonation
RE: stainless steel and ozonation
The stainless part is quite specialised - a piece of capillary tubing - and although I've asked our manufacturers if they make it in other grades (such as those suggested) they have not yet responded.
In the meantime I'm running a few in-house tests (accelerated corrosion then various cleaning methods). I'll post any interesting results.
Thanks again!