Steel corrosion in standard air

[jfaucher]

I'm not 100% sure I well understand the concept of sacrifical anode... someone could help me?

I'm using an all-steel linear bearing in a room where occur standard conditions of air temperature and humidity. In this case, the corrosion of the track is not happening really quickly, but after many years of operation, I may have to replace this really expensive track because of corrosion.

Lets say that this track would not be available in stainless, chrome plated or any other way to prevent corrosion. Could I use zinc or aluminum or magnesium as a sacrificial anode to prevent the steel track to rust over the years? Does the surrounding air, with its normal level of humidity, could be considered as an efficient electrolyte? If not, why does the steel track is rusting?

Thanks!

Jean-Pierre Faucher, ing.

http://www.cel-aerospace.ca

 

[gr2vessels]

The air humidity is condensing on the tracks and is sitting there long enough to start/progress the corrosion process. Simply the CO2 in the air, disolved in the moisture is readily an acidic medium to start the corrosion. Any protective coating, even some grease will slow down considerably the corrosion process. For your confort, there is no material on Earth to be imune to corrosion process, the best has only better corrosion resistance than other materials. Your material for those tracks was selected for economical reasons and should be replaced when is out of spec.
As far as the cathodic protection, you need an electrically conductive medium between the rack and the sacrificial anode to close the circuit. The moist air doesn't qualify as electrolyte.
Sorry, I wish I could give you better info.
Cheers,
gr2vessels

 

[mcguire]

Au contraire, while cathodic protection will not work outside a conductive media, an ordinary, properly selected, stainless steel would not show measurable corrosion in any of our lifetimes.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[gr2vessels]

mcguire,
Nobody would contest your engineering suggestion that long and hard selected stainless steel would work better than carbon steel.
However, please read the OP in full;- 'Lets say that this track would not be available in stainless, chrome plated or any other way to prevent corrosion.' Do you have better answer than 'Au contraire'?

 

[mcguire]

You're right. He simply is asking will galvanic protection work and you correctly answered,"no". He has ruled out changing materials and surface protection, although this would seemingly provide a wealth of possible solutions.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[gr2vessels]

Jean-Pierre,
You could do a service to yourself, by reading a bit on the internet the basics of corrosion fenomenon and corrosion control. It is fascinating, challenging and rewarding, by opening a totally new window in your engineering experience. I could bet that once infected with this virus, the corrosion protection will always be part of your life and lift your skils.

 

[EdStainless]

You can use galvanic protection. The electrolyte is condensation on the surface. We call protection like this galvanization. You put the Zn (or ZnAL) on the surface where corrosion will happen.
On the working surface of a rail this coating will not last. Usually rail surfaces are kept clean by wear and that reduces rapid corrosion rates.

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Plymouth Tube

 

[emxhps06]

Would you consider using corrosion inhibitors?