Cpriester123

So, I've read many forums about engine prep but nothing up to date. Engine is back after the machinist did his work. Yes I know, I should have had it hot tanked. I didn't so now I'm stuck in this position. The engine had maybe 500 miles on it after its rebuild and paint. Pulled it had work done and now it's going back in but before I do I'm stripping and repaintig it. I'm down to bare metal now and I read phosphoric acid can be applied to turn flash rust/surface rust into phosphate to be painted. And let it soak over night. Then wipe clean next day with wax, degreaser, acetone or lacquer thinner. Then paint.....My question is, has anyone here ever did this before or had experience with this. How well did it work?

Tedd Thompson

Back in the day I sold a few thousands gallons of the stuff (various manufactures). What it does is convert red oxide (rust) to a black oxide coating which in it self is a rust preventive and a good foundation for paint.The good part of phosphoric acid is that its properties don't linger after it drys like so many other acids do and it's not as toxic as hydracloric (muratic acid) which will burn the heck out of your skin.And yes it works fine maybe not as good as sand blast and epoxy primer and top coat finish but a lot quicker. cheaper too... Tedd

Cpriester123

Have you heard of any successful stories of using epoxy primer AFTER the acid?

Tedd Thompson

The acid becomes pretty much a neutral coating and the film it leaves would have no affect on anything put over it whether epoxy or alkyd primer. My experiance involved industral coatings and few epoxie primers were used mostly because of the size of the projects and the added cost of product but when they were used they worked as expected.. Tedd

MDchanic

Phosphoric acid is the same as MetalPrep and similar surface prep agents.

Just dilute it and use it according to the instructions for any of those.

I like to apply, wire brush, rinse off, and dry, but some instructions dispense with the "rinse off" part.

- Eric

davebw31

I use a product called "Extend Rust Neutralizer" made by Loctite. I use to buy it by the case (12 spray cans in a case) since it was cheaper and I used a lot of it for restorations. It also comes in a liquid. I liked the spray cans as it was easier to use and I thought it did a better job in coverage!

I sprayed two light coats, waited 30 mins. and then sprayed one heavy coat to make sure it gets in to every "nook and cranny". Let it dry for two days, in low humidity and at least 70 degrees temp. (or higher). It is a water based product that acts as a catalyst, reason why I wait a minimum of two days to let it dry thoroughly. It also is a very good base for painting and adhesion of the paint.

I did all of my chassis, engine block etc., and brackets in 2000 for my 70- F-85 and they all still look like I did them yesterday!

Cpriester123

Appreciate the feedback. After the use on an engine, did you use any primer before painting the engine. If so, what type of primer? Epoxy or etch?

Cpriester123

Thanks Eric I appreciate it

Cpriester123

Thanks Tedd I appreciate it

davebw31

NO, I did not use any primer. Reason why I liked this product, as you do not need a primer to top coat with paint. The important thing is to handle the piece you want to per treat with Extend is to not use your bare hands and using compressed air to blow off any residue from bead blasting and also let it dry completely. Handle with nitrite gloves.