Sand Blasted an engine bay

General Discussion. Make yourself at home...read, ask and answer!



Non-Lurker
Posts: 7
Joined: Tue May 03, 2022 3:53 am

Country:
USA
PostPosted: Tue May 03, 2022 4:36 am
I need help please. So i read serval users use "phosphoric acid and a scotchbrite" to clean and prep the surface.

Do i do A or B

A: Work TINY areas strip that metal as CLEAN as possible and hit it with my Epoxy 840R ASAP With no Rust convertor, Maybe some Wax and grease remover after Sand blasting the metal and that's it?

B: Strip the whole bay knowing i'll get surface rust, Then come back using Septone Rust convertor over the entire job then coating it with Epoxy 840r.

PROBLEMS; I've done this entire job once already. As it's a big job i stripped the entire bay knowing i'll get some rust, Long story short i used this "Rust convertor" that was thick.. I even rang the hotline on the product the guy told me i won't regret using it. Well i did, Everything he told me was ****. It's a "non sand" type of convertor that turned Purple or black he said i could pour it where ever i wanted which is exactly what i wanted to do to make sure everything was converted especially the hard to get places in the engine bay.

It ended up having major adhesion issues where ever the product was to thick etc it did not like it to be fair %80 of the epoxy was hard as a rock no way it was coming off but i didn't want to go through the heart ache a year down the track %10-20% of the paint job has completely disappeared lol it would of happened i have no doubts, So lesson learnt don't use that **** convertor that you have to leave on the metal i didn't like the idea and i should of stuck to my gut feeling or atleast i should of sanded it off

So this is why i'm asking this is a BIG job and i'm doing it for a second time.. If i had a BIG **** compressor i wouldn't be asking this question because i'd just strip it %100 clean and spray it with epoxy, But my compressor is still it takes a long time to sand blast and get it %100 clean.

So can i sand blast the bay, and get it "Pretty clean" but not %100 clean, Let's say if there is some tiny surface rust still on the job and i spray Epoxy 840r over it, Will it kill it like i've read it can? Once that little bit of rust is covered it should die?

If so, I might have to go get some more Blasting Media and isolate area's at a time, Blast that metal %100000 clean then Epoxy 840r it

Or Should i use the Septone rust convertor? Problem with that is, It's hard enough to sand blast some of these area's let alone > Put Rust convertor on > 30 minutes > Remove with a Damp rag > Remove with W+G Remover > Paint so it's a 4 step Rust convertor.. And like i said there is some really really hard area's.. I know i won't be able to %100 do the prep/requirements in these area's it's just near impossible.

So what do i do, Forget the rust convertor all together sand blast it spotless and just epoxy it? Do i maybe use the rust convertor on the big area's i can easily get to so i know they are %100 rust free then coat them, Then Sand blast the hard to get area's then coat them ASAP?

Thanks i really don't want to do this a third time i feel like the best option is just sand blast %100 clean > Epoxy but i just know i won't have enough media to sand blast this whole engine bay so there is no visible rust but i want to do this properly.

User avatar

Top Contributor
Posts: 2762
Joined: Sun Dec 16, 2012 4:46 am
Location: Canberra
Country:
Australia
PostPosted: Tue May 03, 2022 6:03 pm
Forget the Septone rubbish. Clean the metal by blasting as much as you can. Apply 1 coat of 840R as a sealer. Proceed until entire area done. Then scuff and apply 2 coats of 840R. These can be sanded or you can apply using the non-sanding mix and top coat straight over, as long as you stay within the application window.
Chris



Top Contributor
Posts: 6735
Joined: Tue May 19, 2009 7:10 pm
Location: OREGON COAST
PostPosted: Tue May 03, 2022 7:54 pm
I'd throw that love potion away or return it if posible. how long is it going to take you to blast the complete engine bay? ever think about renting a higher output air compressor? your doing this outside i presume? what kind of weather are you haveing during this operation?
the reson i ask, is it posible to blast say half or a third in a day? and if the weather is good? you might try and blast a section then cover it with an old blanket, wrap it tight then cover that with some visqueen. the next day do the same until your done. then paint the hole thing at one time. a little light surface rust is going to be ok in your situation.
Jay D.
they say my name is Jay



Non-Lurker
Posts: 7
Joined: Tue May 03, 2022 3:53 am

Country:
USA
PostPosted: Wed May 04, 2022 4:48 am
badsix wrote:I'd throw that love potion away or return it if posible. how long is it going to take you to blast the complete engine bay? ever think about renting a higher output air compressor? your doing this outside i presume? what kind of weather are you haveing during this operation?
the reson i ask, is it posible to blast say half or a third in a day? and if the weather is good? you might try and blast a section then cover it with an old blanket, wrap it tight then cover that with some visqueen. the next day do the same until your done. then paint the hole thing at one time. a little light surface rust is going to be ok in your situation.
Jay D.


Yeah i rented a bigger compressor, I ended up spending the whole day and blasting everything then i hand sanded everything, I was pretty happy with the result but i will admit there was some tiny tiny surface rust here and there, I tried to get anything with hand sanding, But i just know there was %100 some rust still within the metal i just really hope the Epoxy does it's job and hopefully prevents the rust..



Non-Lurker
Posts: 7
Joined: Tue May 03, 2022 3:53 am

Country:
USA
PostPosted: Wed May 04, 2022 4:54 am
NFT5 wrote:Forget the Septone rubbish. Clean the metal by blasting as much as you can. Apply 1 coat of 840R as a sealer. Proceed until entire area done. Then scuff and apply 2 coats of 840R. These can be sanded or you can apply using the non-sanding mix and top coat straight over, as long as you stay within the application window.


Okay i followed you're advice, I sealed it with 840R got the job done.

That was the hardest thing in my life, I regret taking an engine bay back to metal to the extend i did.. I thought i was doing the right thing.. Making sure there's no underlying rust then i just kept chassing all these little places everywhere, That was a nightmare. I really hope i got everything blasted & sealed really nice. It's playing on my mind i tried my best... I will admit i took on way to much i should of isolated sections from scratch and sand blasted a section and sealed it. Did the engine bay in like 4-5 sections. Yeah it might of taken me a few days but i'd feel much more confident with the process

I've got a question, So I got a Sealer coat with the 840R

I used the Sanding mixture, It's going to rain here for a while so i'm not sure when i'll be able to attack this again to finish it

Then from there you wouldn't worry about a high build primer? Or any 2k Primer? I thought it was kind of good practice to seal in the epoxy with another primer but is it just wasting money? because honestly i'd rather let this Epoxy cure then give it another nice 2 coats like you say and make sure everything is sealed as best as i can, I'll use the Sanding mixture so then i can sand that epoxy down really nice and flat for the base coat.. So yeah if primer is not really needed i won't worry about it.

On the TDS the Non-sanding ratio shows (Primer | Primer Surface) Showing that it seems like the tds says Expoy > Primer > Base. Is that correct?

But then the sanding ratio shows just
"Centari 2K Topcoats
Centari Basecoats
Cromax Basecoat"

So does that mean that the Non-sanding one does need a primer? But the sanding one does not? Bit confusing. I just want to make sure i've done this right this is a ton of work

Thanks so much for the advice.

EDIT : I just read i can apply the 840R with a brush aslong as i use NO activator, So i'm going to get up ASAP tomorrow get the metal up to temp and see if i missed any places and give it a nice little coat with a brush. It was a very long day so i'll check in the morning ASAP.

My question here is, Say i missed a little bit do i just scuff the Epoxy around where i missed? Then give it a brush or can i just brush the 840 straight on?

Reason i ask is because i don't want to sand the Epoxy to early, But i know once it's dry it requires to be sanded for proper adhesion to the coat underneath. It says "20 °C 12 hr - 16 hr" So it will be 20c and it will be about 16hrs the time i'm ready to apply some more Epoxy so technically i should scuff up anything i'm going to cover as it's pretty well dried ready for sanding after 16hrs, Correct?

User avatar

Top Contributor
Posts: 2762
Joined: Sun Dec 16, 2012 4:46 am
Location: Canberra
Country:
Australia
PostPosted: Wed May 04, 2022 3:25 pm
Times are a guide. If you're at 16 hours and 3 minutes then not scuffing will be fine. On the other hand, scuffing at 12 hours ensures that there is a mechanical bond. What I'm saying is follow the TDS but don't overthink it.

840R is what I'd call a "medium" build primer. Thick enough to give good protection but, if you want that super smooth, "shaved" look in the engine bay then you'd need to have done some work direct on the metal first and then a high build primer or even a spray polyester filler afterwards. All depends on the standard of finish that you want. If you're happy with the metal as is and you're just sanding to denib and take out any runs/peel then do that but watch out in an engine bay where there are lots of spots where you can rub through the 840R. A little scuffing before you brush on the epoxy over missed spots or rub-throughs is a good practice.

I usually tint my 840R if I'm going to do multiple coats or I'm going to top coat straight over it. So, If my finish is going to be silver then I put the first layer on white then the second layer tinted (up to 10%) with a Cromax black tinter (AM5 or AM6). That way you get a better shading for your top coat and a visual cue that you've sanded too far.

You can apply top coats straight over 840R. Epoxy is the best "glue" between a substrate and base or direct gloss that you can get. In your case you've applied a "sealer" coat of sanding mix 840R. Your plan to put another 2 coats on later and then top coat will be just fine. As above, high build primers are for getting super flat surfaces and actually detract from the performance aspect of a coating system, i.e. being so thick they don't always flex with the metal whereas what you're doing is much better. Epoxy stays quite flexible and keeping the dry film thickness down is, in my book, one of the keys to getting a coating system to perform in the long term.
Chris



Non-Lurker
Posts: 7
Joined: Tue May 03, 2022 3:53 am

Country:
USA
PostPosted: Wed May 04, 2022 7:12 pm
NFT5 wrote:Times are a guide. If you're at 16 hours and 3 minutes then not scuffing will be fine. On the other hand, scuffing at 12 hours ensures that there is a mechanical bond. What I'm saying is follow the TDS but don't overthink it.

840R is what I'd call a "medium" build primer. Thick enough to give good protection but, if you want that super smooth, "shaved" look in the engine bay then you'd need to have done some work direct on the metal first and then a high build primer or even a spray polyester filler afterwards. All depends on the standard of finish that you want. If you're happy with the metal as is and you're just sanding to denib and take out any runs/peel then do that but watch out in an engine bay where there are lots of spots where you can rub through the 840R. A little scuffing before you brush on the epoxy over missed spots or rub-throughs is a good practice.

I usually tint my 840R if I'm going to do multiple coats or I'm going to top coat straight over it. So, If my finish is going to be silver then I put the first layer on white then the second layer tinted (up to 10%) with a Cromax black tinter (AM5 or AM6). That way you get a better shading for your top coat and a visual cue that you've sanded too far.

You can apply top coats straight over 840R. Epoxy is the best "glue" between a substrate and base or direct gloss that you can get. In your case you've applied a "sealer" coat of sanding mix 840R. Your plan to put another 2 coats on later and then top coat will be just fine. As above, high build primers are for getting super flat surfaces and actually detract from the performance aspect of a coating system, i.e. being so thick they don't always flex with the metal whereas what you're doing is much better. Epoxy stays quite flexible and keeping the dry film thickness down is, in my book, one of the keys to getting a coating system to perform in the long term.


Thanks so much

Yeah as i've done this whole engine bay twice that was my initial plan. I did the Epoxy 840R sealer then i did some real light bog work i think i used mainly fiberglass as i heard bog will be more likely to crack with flex in the bay so i didn't want to go overboard it came up really nice then i found the adhesion issues.

So this time round, I've got the sealed 840 now i'll probably apply some light fibrelgass to flatten out some of the little bits and pieces to get it flat, Then i'll spot them with 840r Then apply the 2 coats.

Only question i got left is, Okay like u say the high build is detracting performance away from the Epoxy which makes sense,

So as this is a somewhat "Show room car quality" Could i achieve similar results with 840r? Surely i could put down a nice good 2 coats and then just Focus on what's visible and try get that really nice and flat? I remember sanding the Epoxy and i couldn't believe how well it sanded when fully cured and it came up really nice.. But i didn't apply a base over it to really see "how nice it looked"

What's you're advice there for show room quality, Forget about the high build primer and just work with the 840r? Like i'm really not extremely fussy i want a nice job but the engine bay does not have to be like a mirror, So now im question do i suffer performance and put a coat of high build on to work with that just in the main engine bay area only?

Return to Body and Paint

Who is online

Users browsing this forum: Google [Bot] and 124 guests