Spray painting over existing paint - do I need primer?

[Engram]

I'd like to spray some steel desk legs. They're already painted (from the factory) in a rather fetching shade of brown.

The paint also has a slightly bobbly texture.

Will I need primer or can I lightly sand and then spray new paint?

 

[badcompany]

lightly sand and spray away.

 

[Engram]

lightly sand and spray away.

Ok, that's what I was hoping. Have you done this before?

 

[Maximum Triceratops]

If they are table legs then chances are they will take a knock or two, sand them down as said already with a fine sandpaper, spray them with at least two good coats then spray them with a clear laquer tfor a little bit more protection.

 

[Lopéz]

Keying the surface will almost always be sufficient. Use a Scotchbrite pad, or if you can't get one of those, a green scourer makes a decent alternative.

 

[Makhaira]

Should be absolutely fine. I'd either just key as mentioned above, or if they're already significantly dirty, wash down with a light detergent solution and rinse off with hot water, dry, and THEN key with fine sandpaper.

 

[arctine]

Sand, add a layer of primer, sand, add a second layer of primer and then give it a few coats of paint and lacquer.

 

[Engram]

Thanks for the advice guys. In the end I did use primer because I accidentally sanded down to the metal in a few places!

It remains to be seen if the black paint will stay on there, but it looks good at the moment.

 

[orbspeed1]

Primmer changes the colour of the top coat, Ie you would not use a red primmer with white paint you would use a white primmer.
You always try to match or compliment the top coat with the primmer.
If you were spraying a galvanised or copper or brass surface you would use a etching primmer and if it was plastic you should use the correct coloured plastic primmer as its more flexable.