Here's what they do on a lot of the steel crabbers and i've used it on my old boat trailer and hydraulic valves. Trailer was 13 years old and the steel looked like new. Wire brush, brush on Ospho
Wire bursh all the loose rust then give it a coat of a product called "ospho" here's part of the directions from the website
RUSTED METALS - OSPHO is a rust-inhibiting coating - NOT A PAINT You do not have to remove tight rust. Merely remove loose paint and rust scale, dirt, oil, grease and other accumulations with a wire brush - apply a coat of OSPHO as it comes in the container - let dry overnight, then apply whatever paint system you desire. When applied to rusted surfaces, OSPHO causes iron oxide (rust) to chemically change to iron phosphate - an inert, hard substance that turns the metal black. Where rust is exceedingly heavy, two coats of OSPHO may be necessary to thoroughly penetrate and blacken the surface to be painted. A dry, powdery, grayish-white surface usually develops; this is normal - brush off any loose powder before paint application.
NEW METALS - For new ferrous or aluminum metals: remove dirt, grease, or oil; apply OSPHO, let dry overnight, then paint.
GALVANIZED - where appearance is important, apply one coat of OSPHO, let stand for approximately thirty minutes or until metal is etched. Flush with water, avoiding damage to adjacent areas; or wipe to a smooth finish, let dry, then paint. Where appearance is not important, one coat of OSPHO is recommended to thoroughly coat and etch the metal. Let stand overnight or until completely dry. Brush off any loose powder before painting.
A typical paint application will last much longer after an application of OSPHO because subsequent paint coatings attach themselves so tightly that moisture and oxygen cannot attack the metal. OSPHO is water-thin, and therefore goes on easily and covers a larger area than paint. One gallon covers approx. 600 square feet. Historically, best results have been achieved using an oil-base primer and topcoat. Test a trial sample before using under epoxy or latex-base paint applications. OSPHO is equally effective for exterior and interior work alike and is highly recommended as a pre-treatment coating by leading paint manufacturers.
THEN TOPCOAT WITH,
Kel-Kote Formula 206 is a high build, highly abrasive, resistant coating formulated for long term corrosion mitigation of industrial structures and equipment.
Gloss: Flat. Color: Black Recommended Thickness: 12 MDFT Practical Coverage: 50 square feet per gallon. Reducer: Airless Spray: None required using Kel-Kote application equipment. If necessary, use water not to exceed 15% by volume. Pot Life: Unlimited. Dry Time: 4 hours at 60Ã‚ÂºF, humidity 40%. Topcoating: When a color coat is desireable, use Kel-Kote Formula 105 or Kel-Kote Formula 104. Surface preparation: Substrate must be free of all oil and loose paint. Sandblast to SSPC-SPC-6- 63T, Grey Metal Commercial Grade. Prime with Kel-Kote Formula 100. Packaging: Five gallon pails. 55 gallon drums available. Weight per gallon: 11 pounds. Flash Point: None. Mixing: Mix thoroughly to a homogenous state. Solids By Volume: 56%. Application: Spray, brush or roller. Clean Up: Clean water. Caution: Protect from freezing.
I used to use Pettit Rustloc,it lasted better than most.You have to do 2 coats minimum and topcoat within 24 hours.I tried coroseal and liked the rustloc better.If you put the top on the can,once it cures you'll never get it back off,tough stuff.I havent tried por15,but heard it works good if you follow the steps for prep.Nothing seems to be as easy as the manufactures say as stopping rust.
i know you use those new fangled light weight diesels thats made of hybrid metals, but i have REAL cast iron ones. were the paint has chipped its rusted for bad stuffing boxes slinging water all over the place.
Thing about rust convertors I find is you just want to remove loose flakes and not sand to bare metal. And it can't be oily or dirty. That's all I did with a wire wheel. Top coat with engine paint. Gear was the worst.
Manifolds and risers were new. New wires, starter and alt. Hobbs did the carburetor. "New" rear mounts from the marine consignment store. Used aluminum pan and valve covers from ebay. But I never even opened that engine up. I was the third owner of that boat 10 years ago. I think everything was original from 1978. Engine always ran great.