# Bare metal needing filled



## Stratf01 (Jun 22, 2018)

I always thought that etch primer should be used on bare metal then fillers then normal filler bit some say use filler them etch primer. 

What do you recommend? 
Seems to me that wet fillers must react to the metal or are there rust preventatives in there? 

Any help and advice hugely appreciated 
Thank you


----------



## steveo3002 (Jan 30, 2006)

fill onto bare metal or epoxy primer ...not etch


----------



## Sh1ner (May 19, 2012)

Filler onto bare metal unless you want filler shrink/lift around the edges at some point later. Can happen quickly or a little more slowly but it always happens eventually.
Etch is really for things like aluminium because of the need to eat through the layer of oxidation present so that the paint sticks to the metal not the oxide.
The oxide layer reforms instantly on aluminium as soon as the surface is cleaned unlike steel which takes a while to oxidise and why normal primers can be used.
It is also why aluminium can be difficult but not impossible to weld or solder.
When filling Aluminium I always roughen the surface more than I would steel then mix the filler, then clean, wipe down and fill immediately.
Car body filler is generally chemical based polyester resin not water based so no need for rust prevention.
Once the clean metal is sealed to oxygen or water there should be no issue but it is important to let fillers dry completely after wet flatting and before painting to avoid any moisture being trapped which will micro blister the paint later.
Easy sand fillers can be quite porous.


----------



## Stratf01 (Jun 22, 2018)

Wow. Glad I asked before buying the stuff! 
Thank you very much guys


----------

