Can I combine primers on aluminium?

[choochoo_balooParticipant @choochoo_baloo]

The original paint on a cast aluminium guard was badly cracked all over and was flaking. It had been built up with high build primer like they always used on 1950/60s machine tools.

Today I applied Normfest aluminium aerosol primer to the scrupulously clean metal. The can makes clear to apply one coat, but says it's "overpaintable".

Can I apply a (ferrous) brush-able high build primer I already have onto this, to build up the layer, since I already have a tine of it?

Wanted to check before diving in! Thanks in advance.

[choochoo_balooParticipant @choochoo_baloo]

[Paul LousickParticipant @paullousick59116]

I am not familiar with the Normfest product but etch primers which contain acid are often used on aluminium to give good bond but can only be used on bare metal. They will not adhere to filler material. Maybe why the instructions say to only apply one coat. Etch primers should be given a coating of a normal primer prior to the colour top coats.

Cannot comment on your ferrous primer without details. Best to find a data sheet for it.

Paul.

[JasonBModerator @jasonb]

Does not look like that is an etch primer or meant to go onto aluminium, more an base coat containing aluminium that is designed as an anti corrosive spray, more like the silver colours "aluminium" wood primer used on hardwoods. See pdf

Better to use an etch primer which will bond better.

Edited By JasonB on 25/05/2020 07:46:47

[Dave HalfordParticipant @davehalford22513]

Nothing says it's a spray intended for aluminium, it does however say Ferrous so you have two steel primers.

Search for alloy wheel primer and you should avoid all the steel primers just with aluminium in it.

[KWILParticipant @kwil]

Upol 8 etch primer is just the stuff for aluminium.

[choochoo_balooParticipant @choochoo_baloo]

Thanks chaps. First line on zoomed image "GB – aluminium primer". Oh wait a minute, are you all saying it's a metallised aluminium in the spray itself, not an etch primer for aluminium?

Oh in that case, yeah I've bought the wrong thing. Bugger. How can I remove it ready for Upol 8?

[choochoo_balooParticipant @choochoo_baloo]

Actually please can we please go back to basics, and confirm my plan of attack:

1. Remove existing Normfest ferrous primer – paint stripper I guess
    
2. One coat Upol 8 etch primer
    
3. 1 or 2 coats of my Selemix brush cellulose high build brush primer, to fill all marks in the rough casting. Datasheet description:

   "fast drying synthetic primer with high filling and good anticorrosion properties.
   It is intended to protect ferrous substrates."

4. Selemix colour topcoat (same family as primer). According to my helpful automotive supplier, it can take a month+ to go rock hard.

Edited By choochoo_baloo on 25/05/2020 12:32:20

[Dave HalfordParticipant @davehalford22513]

1 brake fluid might.

2 yep

3 Cellulose is not synthetic or 1k as it tends to be called now. They don't like each other and will fight, synthetic looses every time.

[choochoo_balooParticipant @choochoo_baloo]

Posted by Dave Halford on 25/05/2020 21:02:07:

3 Cellulose is not synthetic or 1k as it tends to be called now. They don't like each other and will fight, synthetic looses every time.

Not sure what you're saying Dave (I am a novice!) – I shouldn't use this Selemix family on top of the hardened Upol 8?

I used the Selemix on cast iron and it's worked a dream. My main concern is how it'll take to an etch primer.

[Nick Clarke 3Participant @nickclarke3]

Posted by choochoo_baloo on 25/05/2020 23:28:23:

Posted by Dave Halford on 25/05/2020 21:02:07:

3 Cellulose is not synthetic or 1k as it tends to be called now. They don't like each other and will fight, synthetic looses every time.

Not sure what you're saying Dave (I am a novice!) – I shouldn't use this Selemix family on top of the hardened Upol 8?

I used the Selemix on cast iron and it's worked a dream. My main concern is how it'll take to an etch primer.

Cellulose primer is not synthetic primer. They are two different things. Provided you have given it plenty of time to dry you can usually overcoat cellulose primers with synthetic topcoat. You can't safely overcoat synthetics with cellulose, however cellulose topcoat is not as common as it once was.

I suggest your Selemix primer is intended to go straight onto bare steel.

[SillyOldDufferModerator @sillyoldduffer]

Can two different primers be mixed when we're not even sure if one of them is a primer for priming Aluminium or an Aluminium primer for priming Steel?

I don't think ChooChoo's question can be answered safely. Results depend on the chemistry of the two primers. They might be compatible or they might not. As I doubt anyone on the forum knows, the easiest way to confirm compatibility is to try them on a test piece.

If a long-term reliable finish is needed, best to buy new & apply primers, paints and fillers as recommended by the makers. Mixing random products is bound to be risky – pioneer research always is.

Dave

[Dave HalfordParticipant @davehalford22513]

Posted by choochoo_baloo on 25/05/2020 23:28:23:

Posted by Dave Halford on 25/05/2020 21:02:07:

3 Cellulose is not synthetic or 1k as it tends to be called now. They don't like each other and will fight, synthetic looses every time.

Not sure what you're saying Dave (I am a novice!) – I shouldn't use this Selemix family on top of the hardened Upol 8?

I used the Selemix on cast iron and it's worked a dream. My main concern is how it'll take to an etch primer.

This is what you said in point 3

1 or 2 coats of my Selemix brush cellulose high build brush primer, to fill all marks in the rough casting. Datasheet description:

"fast drying synthetic primer with high filling and good anticorrosion properties.
It is intended to protect ferrous substrates."

Which is it synthetic or cellulose?

Cellulose will strip synthetic so the UPol may be at risk, your description does not match a current Selemix product

[Nick Clarke 3Participant @nickclarke3]

I think I can see the problem – If you do a Google search for Selemix brushing primer the first result is a reseller webpage here – **LINK** and the page text does not say what type of paint it is.

However if you click on the data sheet icon on that page it takes you to a datasheet for a totally different product that is synthetic, but for spray application only.

 

Edited By Nick Clarke 3 on 26/05/2020 18:26:34

[choochoo_balooParticipant @choochoo_baloo]

Right now I'm confused. I had been using "cellulose" and "synthetic" interchangeably, but Dave and Nick you've made me realise I need to understand the basics.

(Upol 8 has been ordered anyway – I have to etch prime first regardless).

I'm going to start a new thread to ask about theory. Will then return to this thread once theory has been firmed up!

[choochoo_balooParticipant @choochoo_baloo]

Dave/Nick, following the ever useful input on the other post, here is my updated painting plan:

1) Good coverage Upol 8

2) Selemix "fast drying synthetic primer with high filling and good anticorrosion properties. It is intended to protect ferrous substrates." Get some building up.

3) Selemix topcoat within 24 hrs, especially given the exceptionally warm weather.

[The auto refinisher I bought it from said it's quite fussy about more than 2 coats – doesn't like sticking to itself. So opposite to cellulose practise 80+ years ago my looks of it].

…does this all sound good to you?

[Nick Clarke 3Participant @nickclarke3]

Posted by choochoo_baloo on 29/05/2020 16:46:03:

Dave/Nick, following the ever useful input on the other post, here is my updated painting plan:

1) Good coverage Upol 8

2) Selemix "fast drying synthetic primer with high filling and good anticorrosion properties. It is intended to protect ferrous substrates." Get some building up.

3) Selemix topcoat within 24 hrs, especially given the exceptionally warm weather.

[The auto refinisher I bought it from said it's quite fussy about more than 2 coats – doesn't like sticking to itself. So opposite to cellulose practise 80+ years ago my looks of it].

…does this all sound good to you?

Seems good if it what has been recommended.

Another reason for only two coats of the topcoat might be what we used to call Porkpie-itis – a crusty outside with a soft inside – the paint sets on the surface before the underlying coats if too many applied at once – but follow the expert's advice you have been given.

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