Case Hardened Steel v's Stainless Steel Corrosion Resistance

[prephil]

Hi, Just want to konw is 1075 case hardened steel with zinc immersion coating as good as 316 stainless steel in terms of corrosion resistance.

Also how about 1008 Steel which is zinc plated and chromate dipped v's 316 stainless.

Also, also, what does the term to passivate (stainless steel or any material) mean? Just a short answer will do, nothing too technical if you can.

God bless.

 

[mshimko]

1. General answer #1 - 316 stainless will have significantly superior corrosion resistance compared to zinc immersion coatings.

2. General answer #2 - it depends. What service or environment is involved, and what is the expected service life and corrosion allowance.

3. Passivation in simple ternms refer to the surface of many corrosion resistant metals, such as stainless steels. These metals are not immune to corrosion. Instead, these matals corrode, but the corrosion product is a very thin aned tightly adherring layer that retards further corrosion. The term passivation refers to forming this tightly adherent film. Metals that fall into this category include aluminums, stainless steels, and titanium.

 

[swall]

For stainless steel, the passivation is accomplished by immersion in a 30-50% nitric acid solution.

 

[kenvlach]

1. No.
2. No.
However, depending upon the service environment, zinc-coated steel may suffice. Note that there are different grades (thicknesses) of zinc plating and also several types of chromating. See ASTM B633, 'Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel.'

http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/B633.htm?L+mystore+nuvj7053

Passivation means the process of making less chemically active. W.r.t. stainless steel, it usually means the chemical treatment in an oxidizing solution of nitric acid, with or w/o dichromate, or citric acid, which removes iron and nickel from the surface, creating a more protective surface oxide film largely Cr₂O₃. See ASTM A967, 'Standard Specification for Chemical Passivation Treatments for Stainless Steel Parts'

http://www.astm.org/cgi-bin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/A967.htm?L+mystore+nuvj7053

or the outdated but free Federal spec. QQ-P-35C PASSIVATION TREATMENTS FOR CORROSION-RESISTANT STEEL (S/S BY ASTM-A967 OR SAE-AMS-QQ-P-35)

http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=50793

W.r.t. to zinc plating, cadmium plating, aluminum or magnesium, passivation usually means chromate conversion coating. E.g., MIL-DTL-5541F CHEMICAL CONVERSION COATINGS ON ALUMINUM AND ALUMINUM ALLOYS

http://assist.daps.dla.mil/quicksearch/basic_profile.cfm?ident_number=5499