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Discussion Forums - The Hendrix Group
HomeHomeDiscussionsDiscussionsGeneral Corrosi...General Corrosi...CB7Cu-1 ASTM A747CB7Cu-1 ASTM A747
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11/15/2005 9:00 AM
 
I'm having trouble passivating 17-4 ph. Do you recommend one acid solution over another. Can the copper sulfate test be used to detect free iron following passivation?
 
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11/16/2005 9:00 AM
 
Do Ferroxyl test.
 
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6/19/2006 9:00 AM
 
what passivation treatment would you recommend for a cast 17-4 material? The castings always seem to look rusty following a ASTM A967 Nitric 1 solution.
 
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6/20/2006 9:00 AM
 
As you are seeing Rusty appearance after Passivation ----------- Step1 :- Ensure your 17-4 contains significant Sulphur or not Step 2 : You have to ensure surface is free from embedded Iron particles by Standard Ferroxyl Test. Step 3 : If surface indicates Free Iron first you have to clean and degrease surface from all organic contaminants by Grit Blasting and Degreasing for cast surface Step 4 : You have to do Acid Pickling by HNO3 ( 20%) + HF ( 2%) mix Step 5a :- If your material is NON-SULPHUR BEARING then you do Passivation by 50%by volume HNO3 at 50C - 60C for 40 m inutes maximum. Step 5b : If your material is SULPHUR BEARING then you do Passivation by A-A-A Method ( Alkaline - Acid - Alkaline Method ) as below -- After Pickling soak the part in 5% solution of NaOH at 75 - 80C for 30 minutes ---> Rinse the entire part by DM Water ( < 50 ppm chlorides )spray ---> Immerse the part fully for 30 minutes in a 20% HNO3 solution containing 22 gm / Litre Sodium Dichromate at 50 - 60C ---> Remove from Acid Bath and Water Rinse ---> Again immerse in 5% solution of NaOH at 75 - 80C for 30 minutes --> Passivation is complete. Hope this will work. regards
 
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