Etching primer before Milliput?

[47137]

 

I have built a tender truck from one of Jim Mcgeown's kits and there are some obvious gaps needing filling, especially where the buffers/solebars meet the ends of the wagon.

 

I am tempted to give the model a coat of U-POL #8 etching primer and use this to find all the flaws, then fill them with Milliput, then prime again with ordinary Halfords grey primer.

 

Please, does this sound sensible or would it be better to do the filler before adding any primer? I really don't have a clue - this is only my second brass kit.

 

Many thanks,

Richard.

[SHMD]

Hi,

I have no idea as to the answer but would love to know which way is best.

Hopefully, someone will come along...

 

 

Kev.

[sulzer71]

From previous experience of working in an accident repair centre and having friends in that industry it's common practice to apply etch primer to bare metal before applying filler so maybe this could apply here too?

[Steven B]

If you're feeling brave (there's a risk of unsoldering parts and melting white metal), don't forget that with metal kits you can also fill in holes & gaps with solder.

 

 

Steven B.

[47137]

I have more experience of Milliput than brass or U-POL no.8, so I opted to put the Milliput on first. After this set, it cleaned up from the brass almost too easily, as though it did not really bond beyond some stiction; but it has stayed put where I really wanted it, like between the solebars and their ends/buffer heads.

 

Perhaps, the only things which really stick to brass are solder, Araldite, and cyanoacrylate; and of course the right primer. I tried U-POL no.8 on a piece of brass fret a few weeks ago and it has bonded very well ... I can scrape it off with abrasive paper but not a finger nail.

 

The same primer is now on my tender truck, I will wait until tomorrow to see how well it has adhered to the Milliput.

 

- Richard.

Edited May 18, 2022 by 47137

[SR71]

Not on brass but white metal however I can confirm no reaction between milliput and etch primer if primed after filling.

[michl080]

I have applied a Milliput fillet of about 1.5x1.5mm on plain brass without previous treatment and it could only be removed with brute force. So is you think you'll need the primer to improve adhesion: you won't!

 

It was the white type.

 

Michael

[47137]

My etch primer is now three hours old.

 

I think, the combination of primer over Milliput on brass is going to be fine but I will wait until tomorrow to try some abrasion e.g. fine wet and dry paper. Especially where the primer is showing up the Milliput to be a bit excessive.

 

- Richard.

[47137]

My conclusion is, U-POL number 8 primer is good on brass, solder, steel, Milliput (the green one) and the plastic centres of Slater's wheels. Conversely - when wet, the primer dissolves many model paints - it worked like paint stripper on my spray turntable.

 

The first coat of primer (yesterday) was a bit thin on the interior and showed up some flaws, mostly solder blobs:

 

Today I cleaned these up and added another coat above the underframe:

 

I think this will stay put well on the model.

 

Thanks for the ideas posted above.

 

- Richard.