# Which primer for steel



## Star (Dec 3, 2017)

Hi there, 
my paint shop suggested me to use bi-component primer for my steel frames. The guy only said that bi-component is always better than mono component. 
Durability wise is there a real difference? I can't really find any info on that. 
On top of the primer I will use acrylic paint and clear coat, both bicomponent. 


Thanks


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## FullTiltBoogie (Jan 19, 2012)

2k (bi-component) paint and primer are higher performance paints and there will be a durability difference. On a bicycle application, I don't think a 2k primer is necessary. I use an acid etch primer coat on the bare steel to "seal" it and then spray a high build primer coat over the top that you can sand flat if there are any rough areas. SEM and several other manufacturers make these in a rattle can and they lay nice and flat on clean steel, especially the acid etch.

But....if you already have a spray gun set up with a larger fluid tip for primer, a 2k primer wouldn't hurt!


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## Star (Dec 3, 2017)

FullTiltBoogie said:


> 2k (bi-component) paint and primer are higher performance paints and there will be a durability difference. On a bicycle application, I don't think a 2k primer is necessary. I use an acid etch primer coat on the bare steel to "seal" it and then spray a high build primer coat over the top that you can sand flat if there are any rough areas. SEM and several other manufacturers make these in a rattle can and they lay nice and flat on clean steel, especially the acid etch.
> 
> But....if you already have a spray gun set up with a larger fluid tip for primer, a 2k primer wouldn't hurt!


Thank you, very informative. Do you think a 2k primer will contribute to a better chipping resistance, or that is only a function of the upper coats?


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## FullTiltBoogie (Jan 19, 2012)

That is a good question that I don't know the answer to! Using two component paint/primer will increase "durability" because the second component is an activator or hardener. But I'm not exactly sure what the word "durable" means in reference to 2k vs. 1k because it seems the automotive paint industry places a lot of value on protection from chemicals, weather, and UV. In talking to paint reps, there is never much mention of impact resistance. If I had to guess, Id say the difference would be negligible.


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## Boulder Pilot (Jan 23, 2004)

Durability of a primer? Some primers adhere to bare metal better than others. Some primers sand better than others. All primers will fail if surface prep is compromised. I do not know of a primer that has the ability to add strength to a top coat.


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## bakerjw (Oct 8, 2014)

I always use automotive DTM 2k primers. The one that I've been using lately is HiTeck epoxy DTM. It is a high build primer.

As stated, surface prep is the key.


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