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Rust in hot phosphated parts


We are hot phosphating a FCD400 grade casting after induction hardening on certain zones only. The parts are degreased before phosphating and water rinsed after that.
We are experiencing Rust in very few locations in about 2~3% of parts within a day.
Do you have any suggestions about possible causes and remedial measures?
Will be very much obliged.


Govekar A.V.


Is there further detail on the process, A.V.? If it's strictly home-brew, and RoHS / ELV compliance is not an issue, then a chrome-bearing final rinse might be an easy solution.

Ted Mooney,
Ted Mooney, P.E.
Striving to live Aloha - Pine Beach, New Jersey


We are from LGB, ROLON brand leading automotive chain & sprocket mfrs. in India. We are experiencing the same type of problem.We are doing hot phosphating for two wheeler sprocket where we have a problem of quick rusting in 2 to 3 days even after the application of branded rust preventive oils like dwx32 etc. we want to know whether it is because of chemical qly being used ( G&W)or any process change required. Because this rust we are not getting in all components. only in some of the components. Actually these components are stress relieved & induction hardened. We have seen your msg for 300 hrs for salt spray test. We would like to hear more on this like process detail, cost of operation etc. We are doing around 3 lakhs components / month. your immediate response is highly appreciable.

M.Anandha Kumar


Dear sir,
You should degrease the job properly and after phosphating you can store it in dry acid free process.
Check & maintain proper concentration of solution.
you can also use sealer.

Vishal Duse

adv. saify ind youtube

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