Painting galvanized bolts

[thoner7]

A lot of the bolts on my truck are rusted. I was going to replace them before painting with either Hot dipped galvanized or the shiny zinc.

I know painting over galvanized is tricky, but what’s the best primer or pre-treatment??

some humvee frames Are galvanized so the military must have a process for it

 

[MarkM]

That Galvanic reaction is a real pain. I personally would go with good quality steel bolts. Coat the bolt threads with Permatex Cooper anti seize as well as the mating surfaces of washers used.

Once installed wipe away any anti seize or oil with a breakeen damp rag. Once dry hit with a good primer and paint preferably Rustoleum. Just my .02 cents.

Mark

 

[teletech]

A degreaser like acetone to get the oils out of the coating and then an anticorrosive epoxy primer like PPG 44GN011 or deft 22YO22 (same thing but one is green and the other is yellow)
The paint manufacturers usually recommend letting the zinc weather for half a year or so before paint.
Of course, if you are painting anyway, why replace the bolts? If it's a MV then the odds are the original bolts are of better quality than you can easily buy and if you are painting them anyway, corrosion isn't much of an issue going forward.

 

[87cr250r]

Anti-seize should be called anti-gall. There are much better options out there to prevent thread corrosion. Low strength Loctite, silicone grease, Tef-Gel are all superior options. Loctite can be an ideal choice because it dries which facilitates painting.

You can prep zinc coated fasteners with a quick dip in phosphoric acid. Phosphoric acid is most inexpensively available as concrete etch at the hardware store.

The best option is to locate inorganic zinc coated or zinc-aluminum flake coated fasteners. Some trade names include Dacromet or Armor Coat. This is the system used currently by all automotive manufacturers for chassis and engine hardware.

 

[thoner7]

The bolts are already rusty and it’s easier to replace than to try and de-rust bolt heads.

Phosphoric acid? I’ll check it out, thanks

 

[chucky]

We used to rub vinegar over galvanized metal parts before painting them

 

[MarkM]

We used to rub vinegar over galvanized metal parts before painting them

I've done that also.

Mark