The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Parts rust after phosphating

hi sir
sir I am in need to ask that the after the phosphating how much time is recemended to kept the sheet metal parts as they tend to get the rust
please help me and tell me if any standard is applicable for this

thanks,

Kamran Younas
employ - Pakistan
February 13, 2008

---

February 20, 2008

Dear Younus.
After phosphating as early as possible you can process it other wise you an introduce passivation bath(chrome conversion).

Bhaskar.

Bhaskararao
- Visakhapatnam, India

Phosphate by itself offers little rust prevention. It is the oil or wax or paint that goes on top of it that is the corrosion prevention. Phosphate provides the "tooth" that holds the top coating in place.

James Watts
- Navarre, Florida
February 21, 2008

---

February 29, 2008

Dear Mr.Yunus ,
We need following information to answer your question

1) What type of phosphating you are following
If it is a iron phosphate it will rust quickly and if it is zinc or manganese phosphating than the process of rust development will be slow.
In any case it is advisable to paint or oil the components within 2~4 hours after phosphating.

2) The components you phosphate are they free from rust
3) Rust appears on surface if the baths are not maintained properly.In other words the phosphate coating itself is yellow in colour and it is not a proper phosphating.
Please let us know if you need any further help to resolve the problem.
Regards

Shripad Chitale
- Mumbai, Maharashtra, India

---

Sounds like your bath pH is low, generally the time after phosphating that the parts should be processed is determined by the rate at which the phosphate coating deteriorates(around 24 hrs), not at the rate the substrate rusts. Your chemical supplier will give you the pH levels that you need to maintain.

Sheldon Taylor
supply chain electronics
Wake Forest, North Carolina
March 2, 2008