Why is painting so hard? Even a simple metal bracket.

[Kurtatron]

I’ve swapped an engine, done multiple timing belts, and even learned to weld, but I have never figured out how to paint.

Oh, I’ve tried, but every result has been a miserable failure. Everything I’ve painted, the coat comes off cleanly with a drag of the fingernail. I’ve used different paints, and primers.

My latest humiliation was a simple piece of scrap metal. It’s meant to hold a brake cylinder to my minibike.

I did not sand the piece because the metal is not smooth to the touch. It’s scrap that was weathered to a rough surface. All mill scale was removed using vinegar. Acetone used afterwards. You can see what the scrap looked like before I cleaned it.

I sprayed rustoleum professional primer. One coat, then waited a few minutes, then a second coat. Precisely as the instructions stated.

I waited five days later. The rustoleum sheds paint so easily with my fingernail. . Why is painting so hard? The paint gods would tell me that I need to sand the surface, but how, oh how, oh unknowable ones are you supposed to know when you’ve sanded enough?

I don’t understand why painting has to be so hard. Is there something that can be done to foolproof painting? Some kind of device that reads the surface texture and states your surface is prepped for paint?

GAAAAAAAAAAH.

 

[slacktide_bitog]

Perhaps the vinegar and acetone prevented the paint from sticking. Is it too humid out there?

Do you have any pictures of your painted piece?

Brush loose rust off with a metal toothbrush, and if the rust is still bad, use POR-15 first, before any other primer or paint. Then, use primer, then paint, then a clear coat.

 

[CDX825]

Spray paint seems to be lacking in quality in recent years. I have been painting stuff for years now and never had as much trouble with spray paint as I have in the last few years.

 

[Lubener]

Doesn't look difficult to me. It's as hard as you make it to be.

 

[97prizm]

I’ve swapped an engine, done multiple timing belts, and even learned to weld, but I have never figured out how to paint.

Oh, I’ve tried, but every result has been a miserable failure. Everything I’ve painted, the coat comes off cleanly with a drag of the fingernail. I’ve used different paints, and primers.

My latest humiliation was a simple piece of scrap metal. It’s meant to hold a brake cylinder to my minibike.

I did not sand the piece because the metal is not smooth to the touch. It’s scrap that was weathered to a rough surface. All mill scale was removed using vinegar. Acetone used afterwards. You can see what the scrap looked like before I cleaned it.
View attachment 345000

I sprayed rustoleum professional primer. One coat, then waited a few minutes, then a second coat. Precisely as the instructions stated.

I waited five days later. The rustoleum sheds paint so easily with my fingernail. . Why is painting so hard? The paint gods would tell me that I need to sand the surface, but how, oh how, oh unknowable ones are you supposed to know when you’ve sanded enough?

I don’t understand why painting has to be so hard. Is there something that can be done to foolproof painting? Some kind of device that reads the surface texture and states your surface is prepped for paint?

GAAAAAAAAAAH.

Try zinc chromate. It's a yellowish coating that aircraft manufacturers use.

 

[Snagglefoot]

Etching primer would be my recommendation.

 

[#18FAN]

Sandblast
2k primer followed by a 2k urethane I’d have it looking like a piece of glass in about a hour.

 

[Kurtatron]

Perhaps the vinegar and acetone prevented the paint from sticking. Is it too humid out there?

Do you have any pictures of your painted piece?

Brush loose rust off with a metal toothbrush, and if the rust is still bad, use POR-15 first, before any other primer or paint. Then, use primer, then paint, then a clear coat.

The paint literally drags off the piece with a paper towel. I think it looks great, but man, why can’t it be like commercial stuff that laughs at fingernails?

 

[SC Maintenance]

Spray primer is usually just a lacquer. You need some sort of primer with metal adhesion.

You also should start with a rust inhibitor. As far as something from the internet Jenolite works ok rather than having to go to an industrial place.

 

[wings&wheels]

We share frustrations...

I agree that common spray paint quality does seem to have declined. Without any research, I would guess that certain components used in older paints may not be allowed anymore, but I do not know for certain. That said, spray bombs will never be as durable as a 2K, cured factory finish.

Prep as well as paint quality is key. Wurth is excellent, Rustoleum/Duplicolor are good enough. I just refinished a pair of stainless boat wiper arms using Rustoleum self-etching primer and their textured paint and the finish appears durable but I did not try to scratch it off. It has survived several cleanings with a boat brush though, but I will admit I had somewhat low expectations given the application and stainless. I put hours into the prep w/ cleaners and degreasers (wash, surface prep, glass cleaner then degreaser then glass cleaner). Surface prep was with Scotchbrite pads until an even dull finish then a very quick clean and prime.

I would try again with a good surface prep and etching primer, but be careful with primer compatibility. Good luck.

 

[RDMgr]

Try zinc chromate. It's a yellowish coating that aircraft manufacturers use.

Isn't zinc chromate highly toxic? Doesn't have very low exposure limits? Isn't it considered a significant environmental risk? Isn't it difficult to find over-the-counter? Isn't it designed for non-ferrous metals, specifically aluminum.

Isn't the risk-benefit of using zinc chromate on a piece scrap steel to be used on a minibike heavily weighted against using it?

 

[Cujet]

Zinc Chromate is not tough or fluid resistant. It is also tough to source today.

Bottom line, it is VERY DIFFICULT to find spray can paint OR a non catalyzed can of paint that is tough.

The technology that makes paint coatings adhere well and tough has 2 centuries of refinement.

1) Epoxy primers are what provide excellent adhesion. The 'epoxy' sticks to the surface (so to speak) with excellent chemical bonding.
2) Polyurethane paints with cross linked molecules provide toughness.

You can prep a part all you want, and still get terrible results with a spray can. Conversely, you can take a non prepped metal part, apply self etching epoxy primer (a dip or wash) and top coat with Imron and have it hold up for decades.

 

[Langanobob]

Try baking that painted part in an oven at about 200F for about an hour. I experimented with scratching baked and not baked parts and the improvement was surprising.

 

[DCDG]

prep is key remove all oils from the metal spray with a red metal primer or zinc primer