The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Chromate coating time

Dear sir, I found out that on my galvanized steel which is treated with Passerite 225, it only can stand salt spray for less than 14 hrs. I would like to know whether the contact time period between galvanized steel and Passerite 225 will affect the coating concentration of chromate on the sheet or it is because of the Passerite 225 sludge? Is there anywhere I can have a good chromate coating in which the steel can be coated evenly and on corrected concentration. Right now we are using dipping process in which the contact time is around 4s/cm and is there any affect arise from drying the chromate

richard young
- malaysia
1999

---

1999

Hi Richard,

I am not familiar with the product Passerite but it is probably a chromate conversion coating process. You may like to try the following:

1. Increase the concentration of the passivating salt by at least three to five times.
2. Ensure frequent make up / replenishment of the passivation bath and improve the post rinsing with running water or DM Water.
3. Seal the Chromate coating using sodium metasilicate ⇦ this on eBay or Amazon [affil links] @ 10-20 gms/ litre after chromating.

All this should get the SS up to 36-48 hours and not more. For further information do not hesitate to write to me.

Regards

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

---

Dear Richard,

Further inspiration: Ensure you are using a trivalent Blue Passivation instead of a Hexavalent one. I have just finished testing a trivalent Blue passivation for 72 hours without white rust whereas my older hexavalent one would give me only 40- 48 hrs max.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

1999