H2O2 corrosion protection

[motorone]

Have application for an electric motor being washed down with 30% hydrogen peroxide. Need shaft material that will withstand H2O2. Shaft must be magnetic. Present shaft material is A311 steel. Need similar mechanical properties. I could also plate current shaft with ?? (motor body is aluminum)

 

[Metalguy]

410 SS should work fine, but if you want to plate, make sure you don't have any bending stresses on the shaft. Cr plating should be OK, or possibly one of the nickel platings.

Let's see what Kenvlach says.

 

[kenvlach]

Unfortunately (or maybe not?), I haven’t any experience with metallic corrosion from H₂O₂. My hydrogen peroxide arrives in plastic (PE) & I use it in plastic tanks. An intuitive choice for best corrosion resistance to an oxidizer is an SS that can be passivated in Type VI nitric acid solution of QQ-P-35C. However, these are all austenitic SS, so to meet the magnetic requirement, choose a ferritic SS that can be passivated in Type VII solution. E.g., 17+% Cr SS Types 429, 430, 434, 436, 442, 446 or XM-47 (S44625). Less expensive alternatives with lesser corrosion resistance are the 12% Cr SS ferritic Types 405, 409 and the martensitic Types 410, 414. Also, the 16%Cr martensitic Type 431. The PH alloys may be suitable, but costly. Wouldn’t use a free-machining alloy or the high-carbon 440’s.

Checked some online chemical resistance selectors for materials resistant to 30% H₂O₂:

http://www.coleparmer.com/techinfo/ChemComp.asp

http://www.us.piping.georgefischer.com/external/chemical_resistance_guide/index.html

http://www.astrocosmos.com/pdf/chart.pdf

http://www.titanmf.com/

Results: plastics like PTFE, non-magnetic metals tantalum, zirconium, niobium, titanium and the high nickel alloys.

A survey of half a dozen corrosion books was similarly fruitless: non-magnetic alloys and high Ni- and Si-cast irons.

For general resistance to peroxide in neutral or alkaline solutions: austenitic SS is Normally Excellent, Ni-Resist cast iron is Good to Excellent, and mild & low alloy steel are Good – Suitable when superior alternatives are uneconomical. – Perry’s Chemical Engineers’ Handbook, 6th & 7th Edns.

Specific resistance to 30% hydrogen peroxide: steel has a corrosion rate > 0.050 inch/year at room temperature and above. 12% Cr, 17% Cr and 316 SS’s have corrosion rates in the range 0.002 to 0.020 inch/year at 225^oF for H₂O₂ concentrations to 50%. Nickel corrodes 0.002 to 0.020 inch/year for 100% H₂O₂ at room T. -- Perry’s, 6th Edn., pp. 23-29 to 23-30.

I would recommend the 400 series SS’s listed in the first paragraph. However, depending upon the A311 grade, the ferritic SS’s even in cold-drawn condition may not meet YS requirements. The martensitic SS’s in Q + T condition should exceed A311 mechanical requirements.
Cr plating (over duplex Ni, of course) of the existing alloy should also work, but would require good rinsing after each cleaning. [Actually, good rinsing should be required in any case.]
So, all things considered, end up in agreement with Metalguy’s answer.
Ken

 

[moltenmetal]

Note to future users: the recommendations given above relate to resistance of the material to a wash of peroxide with very specific additional requirements. Peroxide storage and conveyance systems have to worry about more than just corrosion, since iron and copper ions can catalyze the decomposition of the peroxide itself.

A water rinse would definitely be required after a peroxide rinse if people are going to be handling this equipment- 30% peroxide causes painful burns to skin- I've had more than a few of these in my lifetime...