Rattle Can Paint Cure Question

[scratchedup]

Rust-Oleum states "...apply second coat within one hour or 48 hours..."

Can anyone explain this to me?

THX

 

[Bondo]

Ayuh,.... In an hour, the paint will chemically bond to the lower layer,....

After 48 hours, ya sand, then shoot it again,....

 

[countryroad82]

Bondo summed it up short and sweet. Rustoleum has a slow drying time, it gives plenty of cure time.

 

[Stuart in MN]

To be clear, it says,

"Dry and recoat times are based on 70°F and 50% relative humidity. Allow more time at cooler temperatures. Dries tack-free in 2-4 hours, to handle in 5-9 hours, and is fully dry in 24 hours. Apply a second coat within 1 hour or after 48 hours."

 

[bigredmf]

If you coat it between 1 and 48 hours the top coat may attack the base coat so what was once smooth may now be bumpy and uneven.

You can bake it in front of a heating element or heat gun to force dry. I have done this with the heat gun with great success as you can smell the change once the paint is cured.

Red


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[pstnbly]

Most Rustolium is acrylic enamel and uses a slow reducer. Re-coating within 1 hour is inside the re-coat window and allows for a chemical bond. Re-coating between 1hour and 48 hours is outside of the re-coat window and also outside of the curing window, re-coating during this period runs a high risk of the reducer re-activating the partially cured paint causing adhesion issues such as lifting and wrinkling ruining the paint job. Re-coating after 48 hours lets the paint attain a reasonable cure where more paint application will not cause adhesion problems, at this point you are achieving more of a mechanical bond and less of a chemical bond.

Enamel paints cure over very long time spans, months. They produce very durable finishes but are soft initially.

 

[scratchedup]

Most Rustolium is acrylic enamel and uses a slow reducer. Re-coating within 1 hour is inside the re-coat window and allows for a chemical bond. Re-coating between 1hour and 48 hours is outside of the re-coat window and also outside of the curing window, re-coating during this period runs a high risk of the reducer re-activating the partially cured paint causing adhesion issues such as lifting and wrinkling ruining the paint job. Re-coating after 48 hours lets the paint attain a reasonable cure where more paint application will not cause adhesion problems, at this point you are achieving more of a mechanical bond and less of a chemical bond.

Enamel paints cure over very long time spans, months. They produce very durable finishes but are soft initially.

Great info...is chemical superior to mechanical bond? I am a little leery of applying more paint with in the hour since it is a pretty imprecise application process and I dont want too much paint...since it is slow drying.

With this wealth of knowledge is any brand of paint preferable?

 

[Duker]

Most Rustolium is acrylic enamel and uses a slow reducer. Re-coating within 1 hour is inside the re-coat window and allows for a chemical bond. Re-coating between 1hour and 48 hours is outside of the re-coat window and also outside of the curing window, re-coating during this period runs a high risk of the reducer re-activating the partially cured paint causing adhesion issues such as lifting and wrinkling ruining the paint job. Re-coating after 48 hours lets the paint attain a reasonable cure where more paint application will not cause adhesion problems, at this point you are achieving more of a mechanical bond and less of a chemical bond.



Enamel paints cure over very long time spans, months. They produce very durable finishes but are soft initially.

^^^ This.... You can get very good, durable results with Rustoleum or Krylon rattle cans but like most painting - prep and patience are your best friends for those results.


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[calstar]

Can you apply a second coat within an hour and then a third within an hour of that and so on?

thanks, Brian

 

[EdT]

Enamel cures via a chemical reaction between air and the drying oils in the paint. Unlike lacquer type finishes which dry through the evaporation of a solvent, enamels will not re-disolve in their own solvent once they are cured which, as pointed out above, can take a long time. The thicker the paint film, the longer the cure time since the thick film inhibits the availability of air to the lower layers of paint. You can see this if you leave a can of enamel open for a long time. It will skin over where the top layer of paint is exposed to air, but the rest of the material in the can will not harden up for weeks, months or ever (for practical purposes). So, you can probably apply multiple coats within the one hour window over and over, but the resulting film will take a long time to harden. I have had good luck adding some japan dryer to the paint to catalyze the cure and, if possible, heating the part in an oven or with a heater fan or something to warm up the part. Round numbers, a chemical reaction's rate doubles for every 18 fahrenheit degrees so you don't have to make it a lot warmer to see a big benefit in cure time. Warming the part before applying the enamel seems to help too. It also helps to avoid sags in the paint. How hot? I generally go for just hot enough to be uncomfortable to touch. That would be 140-150F. Too hot and the solvents will boil and the finish will be ugly. If post baking after the solvents have flashed off, I sometimes go up to 200F if I'm in a hurry. If you are spraying the paint, I find that you can apply two "coats" in one "application" which helps with the coverage and has only one dry cycle. If brushing that doesn't work too well since the contact of the brush tends to disrupt the original application.

 

[pstnbly]

Great info...is chemical superior to mechanical bond? I am a little leery of applying more paint with in the hour since it is a pretty imprecise application process and I dont want too much paint...since it is slow drying.

With this wealth of knowledge is any brand of paint preferable?

It is best to add coats within the re-coat window to a point for the chemical adhesion. There is a point where to much is a bad thing. Three medium coats is about it for Rustolium, more and the paint may sag or stay soft for a long time.

 

[white6589]

^^^^^^
EdT,

I won't "quote", but that was an excellent explanation.

Thanks

 

[radrush]

Rust-Oleum states "...apply second coat within one hour or 48 hours..."

Can anyone explain this to me?

THX

Ayuh,.... In an hour, the paint will chemically bond to the lower layer,....

After 48 hours, ya sand, then shoot it again,....

It's about "out-gassing".

If you recoat within one hour or after 48 hours then the out-gassing of the curing paint will not affect the subsequent coats.

However, if you wait 48 hours and sand do NOT recoat without waiting an additional 48 hours. Sanding causes more out-gassing

 

[gahrajmahal]

All good explanations, but if it is a better than spray can and Rustoleum finish you are after spray bulk paint using an inexpensive spray gun and your choice of paint will give you better results. I get excellent results using the Harbor Freight $9.95 gun. If you will need several cans the cost is much better too. Also Rustoleum in a quart can sprayed yourself seems to be a superior finish compared to what I can get with the spray can. I think it is because you can use a better quality of reducer.
No compressor? You can use a cheap airless for nail guns etc. when painting small jobs. It will work just fine.

 

[theoldwizard1]

When doing multiple coats you need to increase the drying/curing time. Remember, there is a big difference between dry enough to be handled and fully cured. Curing temperature also makes a big difference. If it is drying in an unheated garage and the evening temps are getting below 60F you had better add another couple of days.

 

[WoodsTruck]

I had to repaint a hood on the kids snowmobile. I started with a plastic hood that was severely weather cracked to the point I sharpened a wood chisel and used it as a draw knife to shave the top layers off. Then used a random orbit sander with 80 grit to get to the bottom of the cracks, worked my way down to 150 in the random, then started on it by hand until I had the plastic down to a 300 grit wet sand finish then started wet sanding the Rustoleum primer until it was smooth. Then I applied up to 3 light/medium coats at a whack let sit for a couple days or a week, then wet sanded and repeated about 6 times. Ended up with a 2000 grit wet sand then started with Rustoleum clear coat and put about 3 coats this way. Finish product looks good for a simple rattle can application.

When completed, the Meguirs drill buffer worked amazingly well to take out the minor scratches from the 2000 wet sanding.

 

[theoldwizard1]

If you are shooting bare metal, especially bare aluminum, I highly recommend Rustoleum Self Etching Primer.

If you are using any alkyd (oil) enamel in a spray gun you can add a hardener to it. Once it is fully cured it is almost as hard as epoxy.

 

[Kevin54]

If you coat it between 1 and 48 hours the top coat may attack the base coat so what was once smooth may now be bumpy and uneven.

You can bake it in front of a heating element or heat gun to force dry. I have done this with the heat gun with great success as you can smell the change once the paint is cured.

Red


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It's not between 1 and 48 hours, it states WITHIN 1 OR AFTER 48 hours

 

[chornback]

It's not between 1 and 48 hours, it states WITHIN 1 OR AFTER 48 hours

That's exactly what he said. He said DON'T paint it between 1 and 48 hours, but BEFORE 1 and AFTER 48 is fine.

 

[IndyGarage]

You can get a great finish on rustoleum if you spray it right.

I just painted something yesterday with their dark grey metallic rattle can, and it looks like a factory finish. First 3 coats of primer - let it dry about 45 minutes. Then first coat of metallic - sprayed thin, almost a guide coat. 10-15 minutes later 2nd coat, little thicker, looking for almost full coverage. 10-15 minutes later 3rd coat of metallic - full coverage. Finish looks like glass.

 

[pstnbly]

If you are shooting bare metal, especially bare aluminum, I highly recommend Rustoleum Self Etching Primer.

If you are using any alkyd (oil) enamel in a spray gun you can add a hardener to it. Once it is fully cured it is almost as hard as epoxy.

Please be careful using hardeners containing cyanoacrylates, these things are bad juju, fullface respirators and long sleeves outside only and you are still taking a chance. A proper paint booth and PPE is best. These chemical will mess you up. That goes for moisture cured polyurethanes like POR too, they contain CAs.

 

[oldskool ron]

I paint a lot with rattle cans an also with the real stuff guns compressor ect but when I do a set of tins for a bike if I use rattle paint I make a home meade oven .in my home I have my own small bathroom which has a door to the outdoor area .I close the door to my bedroom an set up a small heater an let it run on full for a while .I then paint then move the parts to the bathroom an let it go off then after 30 minutes its ready for 2nd coat .
when painting 2pak I paint in my shed then move to bathroom an the heat in room roughly 30 degrees celcius bakes the job within few hours .just my 2bobs worth of input .cheers

 

[EdT]

I believe the hardeners to watch out for are isocyanates. Cyanoacrylate is, I believe, used as an adhesive.

 

[pstnbly]

I believe the hardeners to watch out for are isocyanates. Cyanoacrylate is, I believe, used as an adhesive.

You are correct, same basic compounds though and still bad juju. Isocyanurate

 

[Roberts210]

I have an old convection oven in my barn and I'll often bake smaller pieces in it to harden the enamel.