Best way to protect machine parts from periodic ultrasonic cleaning 3

[NuclearNerd]

We are designing a tool which must be periodically cleaned in an ultrasonic cleaner, which means immersing it in a water-based detergent solution for a few minutes every few weeks. The tool has several moving parts including gears and bushings, and I could use some help determining what is the best material / finishing choice for this application. I could:

a) Use steel gears & shafts with a thin dense chrome plating. In this case, would the chrome cause galvanic corrosion with the steel parts? Electroless Nickel is another candidate plating, but it requires a rather thick coat.

b) Use brass gears & bushings with stainless shafts. I'm still worried about galvanic corrosion here. I could specify a careful disassembly and drying process after the cleaning to minimize the presence of electrolytes in the long term, but regular atmospheric humidity would remain.

c) Cut the gears from a special galling-resistant stainless alloy. This could be expensive.

Am I over reacting here? Is there another choice I'm neglecting?

 

[gr2vessels]

a) Rinse the tool after cleaning and dry it. The chrome is applied to prevent corrosion, not to promote it, so forget the galvanic corrosion.
b) The atmospheric humidity is not an electrolyte to promote galvanic corrosion. You might have to look out for long term condensing of salty humid air near the seashore, but even then you regularly (once a week) rinse the tool in clean water and dry it. You'd wish to live long as the tool.
c)galling resistant stainless alloy???! why not super dupper maxi mega corrosion reflectant stainless steel, that would be the top! Expensive? yes! but you'll be unic in the world with such tool! and you don't have to worry about corrosion ever again!
Now seriously, usually the gears and chrome plating don't mix (unless decorative plating on the visible side of gears). That's the reason the cheap chinese fishing reel lasts no longer than two outings. Brass gears/bushing and hardenable stainless steel shaft sound more technical, if it wouldn't be mixed with the mention of that silly galvanic corrosion (is the tool permanently submerged in an electrolyte to generate POTENTIAL galvanic corrosion problems?).
Yes, you are over-reacting a bit and yes, there is need to read a bit more about galvanic corrosion and mitigation of it.
Cheers,
gr2vessels

 

[NuclearNerd]

I just assumed that atmospheric humidity would be a risk factor for galvanic corrosion just as it is for bare steel parts. Thanks for setting me straight gr2vessels. There are gall resistant stainless alloys (Nitronic 60 and gall-tough), but they are expensive. I think you've saved me that headache!

 

[btrueblood]

These are exposed gears, or enclosed? Can you spray or brush a little oil on them after cleaning? I guess if the part (with brass gears as gr2 suggests, I'd not use plain steel nor would I expect plating on a gear to hold up at the meshing surfaces) was put away wet, with a cheap cleaning detergent containing a lot of salt left to dry on them, you might worry about some green corrosion on the brass parts...but I'd just wipe it off and move on. And use a better cleaner afterwards. An alternative to oil would be a quick rinse in alcohol, or spray application, to displace residual water more quickly, and stick it somewhere warm to dry out more quickly.

 

[unclesyd]

Parts that are used in the forming of Nylon filaments are
cleaned using a Pyrolysis Oven and the residue left from the
inorganic polymer additives are removed in a very powerful
ultrasonic bath using material like Oakite Rustripper.then get an ultrasonic bath rinse using deionized water. Some parts are force dried while others are air dried. We have three cleaning tanks and 2 rinse tanks with transducers in the cleaning and rinsing solution. You can use Rustripper or similar materials smaller units also.

The parts are made from 440C SS, 430 SS, 316 SS, AISI D@, AISI AR, AISI H11, and various other low alloy steels.

One caveat when using powdered alkaline cleaners is that a lot
of people are sensitive to the dust, especially the ones containing Sodium Metasilicate.

 

[tomwalz]

You can't be the only one with this issue.

Have you tried contacting the solution suppliers?

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.

 

[btrueblood]

Tom raises a point. I do know that a good phosphate bath (e.g. trisodium phosphate in water) as a final dip will dry without flash rusting on steel, or green corrosion on brass. The pH stays high as the solution dries. But, you will have powder residue from the phosphate salts left on the parts. Oh, and a waste stream of high-phosphate water to dispose of.

 

[unclesyd]

Here several ways to protect finished metal from atmospheric corrosion.
1: Cortec has a vapor phase inhibitor system that will cover cases. You can store the parts in bag or cabinet.

2: Dow Corning has Molykote Metal Protector fine finished surfaces, like bearings and gears. One good thing about this is that it doesn't require removal before use.

3; Holdtight is a material used for white blasted metal to prevent flash rusting.

http://www.cortecvci.com/index2.php

http://www.dowcorning.com/applications/search/products/details.aspx?prod=01931318&type=PROD

http://www.holdtight.com/index.html