Spray Painting Your Machine!

[HMF]

Here is a topic we haven't covered!
Painting experts front and center, please!

You tried spraypainting ome parts last week using Tremclad 'Professional' enamel paints, but the paint is still dentable with a fingernail. You even tried putting the parts in front of a heater for a few days with little effect. The paint says to wait 10 to 20 mins beween recoats, with a max time of 1 hour or wait 48 hours. Did the following with the part in front of the heater, so it likey got 20~30c air passing over it. Painted 3 layers of primer, with 15 mins wait time beween, The coats where think enough to have good coverage, but not quite 100% coverage with each coat, more like 75%, so no runs. Waited about 10 extra mins for the paint to dry, then fliped the part over. Painted the back side with 3 coats of primer, 15 mins inbeween coats. Waited about 10 extra mins for the paint to dry, then fliped it back over. painted 3 coats of black, 15 mins apart, about the same coverage as the primer each coat. Waited about 10 extra mins for the paint to dry, then flipped it back over. Painted 3 coats of black, 15 mins apart, about the same coverage as the primer each coat.

Basically, you put 3 coats of primer on each side of the part, and then 3 layers of black semigloss topcoat, with about 55 mins beween primer and topcoat. Even after 25 mins, the primer still not fully touch dry, and where the primer contacted the block it rested on, it riped off on the next part flip. You think you have have to suspend the parts and paint both sides at once.

The main issue with the resulting job, is its just still soft even after a week of drying infront of a space heater.

Questions:

Should you have used thinner coats? It seemed pertty much 100% coverage after the 2nd coat, but I put a 3rd on to insure it was thick.

You want a durable paint and assumed thickness+number of coats is the way to get it. Is that wrong?
Should you wait the 48+ hours recommended after X number of coats? What is X number? Should you wait even longer?

Should you do less or thinner primer coats and let it dry before topcoat?
Does a primer even need 100% perfect coverage or should it be more like a very light, slightly spotty coat?

Thank you!


Nelson

 

[HSS]

Opinions will definately vary, but I don't use primer on bare CI. Clean the CI spotless then I spray the metal with metalprep, which is a sprayon metal cleaner. I painted my SBL with an alkyd paint. If you use primer then paint, a ding will cause the paint to chip off of the primer. The primer sticks really well to clean and prepped CI... well, so will paint if you leave off the primer. IMHO

Pat

 

[StonewellMark]

HSS is correct by saying to clean it spotless. Oils are a paints worst enemy (don't believe me, walk into a body shop paint area with a bottle of Armour All and see if you make it out alive) I prefer to use primer but just use one light to medium coat more as a guide coat so I can see shadowing and texture a little better. Let the primer DRY, at least 1 hour, then top with 3 medium coats that have flashed and are dry to a very light touch. Oil based/spray paint dries by emiting the solvents that carry the paint solids to the item to be painted, if the first coat isn't dry enough IT will never be able to dry properly because the next coat dries before the 1st and basically seals the solvents into the 1st coat, ie.: soft paint . Well this is what I've picked up from my friends body shop, hope it helps. Best of luck!

 

[pjf134]

Clean is the way to go for all painting, even finger marks will leave oil. No primer on cast will work. I have painted stainless and aluminum using martin seynor tripple etch with a lot of success, never tried it on cast, but might work. Rust-o-lium being sprayed on takes forever to dry, I guess it is oil based. I have used a rust inhibetar as a primer and seems to work good. I have been pondering what paint process to use on my lathe, still researching different ways.
Paul

 

[GWRdriver]

The best (most tenacious) home painting results I've ever had were prepped by scrubbing the castings in hot soapy water (dishwashing liquid detergent) with a stiff plastic bristle brush, followed by a thorough hot water rinse and drying. IF I was going to apply casting filler I did that next, followed by sanding down to almost bare metal again, followed by another detergent scrub/rinse/dry cycle. I follow this with a thin but covering coat of a good automotive self-etch primer (I use Sherwin-Williams GBP-988), then I paint. Obviously it will be difficult or impractical to treat large castings in this way, but most of my stuff is relatively small although I did do a Burke #4 cast iron base cabinet (but never again.) Also, I just posted a description of the paint I'm currently using in the Lathes secton.

 

[GWRdriver]

MEK will get you very stoned

I bought some MEK just yesterday at my local H-D and got carded! After I proved I was (probably) a responsible adult the cashier said "Have a great afternoon" and with a little snort I said "I PLAN to!" ;D Anyway, thanks for the tip, I'll have to try that soon.

 

[Tony Wells]

If you like PVC cement, you'll love Methyl Ethyl Ketone. Hard on the brain cells.

 

[pjf134]

I used to use tolulene in a shop in the mid 80's, worked good for cleaning, but would get you high in no time, I used to use a mask when I used it in a confined area with a fan also. It was kind of a laquor thinner smell. I think I lost some brain cells there. That's my story and am sticking to it. I think they banned that stuff now it dryed real quick also, which would be good for painting I think.
Paul

 

[Tony Wells]

Toluene, or Toluol (old name), is still available. Primary solvent in old time model airplane glue. I used it working in a hydrocarbon lab to clean my still. 10 litres at a time.

 

[pjf134]

Tony,
We use to buy that stuff by the drums, since everybody in the shop used it for cleaning and prep work before welding. Come to think about it model glue did smell like it. Model glue is what kids used to sniff a long time ago if I remember right, and they said it caused brain cell damage. If they still sell it would explain why people do crazy things, just a thought.
Paul