first time painting - should I grind off the thin surface rust or just apply rust converter?

[Sberry]

On a rusty piece of iron that has been polished to a shinny bright finish will have rust in the boundaries.

Egon

So whats this got to do with putting a little color on a farm implement and wtf would production car painting or some kind of alloy crap have to do with it?

 

[Sberry]

Since you are going to leave me guessing I would say engineer.

You have absolutely no knowledge of what my involvement with rust or corrosion has been!

Yes, absolutely true.

 

[Sberry]

Here is what I am trying to get at and it's easy to get sidetracked and my apologies to the other posters.
I dont always follow my advise. But I am a career welder and have a quasi shop. I been at this a while and did a lot wrong and waste a lot of time where I wasn't paying atnn.
With some of the posts we can only guess. Same with responses and doesnt mean all that ain't good but it's at the risk of confusion at best and most interested are first timers.
Despite being career I dont know much about it.

 

[Sberry]

Egon probably knows more about it,, and paint and rust than I ever will. Here is the difference . I guess some but put myself in the OP position.
He us a fine fabricator and a good welder and he OWES it to himself to paint a little. Start simple, get a few supplies and like most trades once you do a little it's not so scary.
When you get contrary advice consider the source and dont mean that as an insult but perspective.

 

[Sberry]

Guy next town over is a good fabricator and I wouldn't have a problem paying the bill.
I get some of his fab work though. My finish is better and so far they have not blinked when I charge for paint. I separate the bill and itemize some, real basic though. Having hot hi pressure wash is such a boost.

 

[Sberry]

I am a super grinder and sander, got fast at it over the years and clean without thinking about it and ready to go to paint or sandblast if it is. I can sane with a common 4 1/2 and hard wheel and clean splatter, round the corners a little often so subtle its not noticeable I worked on it, 7 inch air sander too, on occasion wire wheel too.
But,,, paint runs off sharp edges and I scuff them smooth and put a little "land" on them, real subtle and splatter sticks up thru paint. It starts to rust day one. All this is a habit so to speak but the customer doesnt care about all the science, when a knob sposed to work it does and I charge extra, I get to bump an hour for touching up the paint on the engine etc all they see is what they can see.

 

[Sberry]

They do notice certain things and not science buit, if its the right color, if its over sprayed, dont get paint on the tires or cylinder chrome or even the cyl if its sposed to be red on a green machine, belts and hoses not to be painted. They notice sharp edges and a wire they cut themselves on. One super deal is to touch up the knobs and fittings with a little color, I paint a green one recent and paint the little handle ends, just the balls on the hyd handles black, really hits them in the eyes as does the fresh red I sponge on the cylinder.

 

[Sberry]

Paint a lot like welding, dont need to know everything about it to do a good job, most of it is simple work, the difference between those take a couple minutes and those with fugg it attitude. Its really not that complicated and shouldnt be.

 

[scaredychicken]

DITTO !!!
OSPHO first, then paint and primer.
No need to sand anything there.
OSPHO will adhere to that very light surface rust even better than absolutely clean steel.

I've never even seen or heard of that stuff - I'll look for it now

 

[Renze]

I grind with grid 36 paper wheel, then wire wheel, then soak it down with cheap thinner in the spray gun till clean thinner drips off it. Then wait till the thinner evaporates and apply paint.

Rust converters i only use when its too darn hard to get it clean, and the subject isnt worth sandblasting.