KRUD KUTTER MR32 The Must For Rust, 32-Ounce Trigger Spray

I bought this to clean two steel hollow rods used on a radio antenna system. The Antenna was bought second hand and while 90% of it was aluminum those two 10 ft rods were steel and had been left outdoors on the ground for 5 years. Yep they were completely rusted and flaking.Taking them out to the driveway I wire brushed off all the flaking rust and then applied the Krud Kutter. The problem with doing large parts is that you cannot soak them in a container so you have to just spray them then let it sit for 30 minutes and then spray them again because the Krud Kutter will dry out. After 4 applications with an in between wash after the first two and then a final hosing off I had clocked about three hours working on them.The end result was at first a mixed bag of very clean shiny galvanized metal and patchy areas of darkened metal.On closer examination I realized it was not rust but just a left over stains that might come out with more soaking time. I decided instead to just use some 250 grit sand paper and rub it down lightly for 5 minutes. The once completely rusted surface was now 90% smooth and was left with just some small 1mm round pock marks on 10% of the surface from deep rust penetration.After cleaning off the rods with pure Alcohol I quickly sprayed the surface with cold Zinc spray. You really need to put something on the surface fast because if you leave exposed you can see a light powdery rust layer forming within minutes.After the cold zinc was sprayed and it dried I was shocked that I could clearly see the part numbers stamped into the metal, they looked as clear as if it was new! These were not even remotely visible before the treatment and I am pretty sure if I had used a hard sander they would have been rubbed out along with a lot of the surface steel. After giving the cold Zinc 48 hours to cure I used an epoxy paint that would hold to the cold Zinc Primer. The end result was almost a factory look as the paint filled out any tiny pits that were remaining.I am very happy with this product, it does what it says it will do and is better than any rust removal chemical I have used before. It does not eat at the metal, only the rust.

I used this on the frame of a 1960 Ford F100 Panel Truck and it had a lot of rust, not quite pitted on the entire frame but in a few areas. As well as on the undercarriage of the body.The trick is to keep the surface you are treating wet with the Krud Kutter. It is a phosphoric acid-based solution so if it evaporates, it will lose its effectiveness and stop working. The "white" that some people are complaining about is actually product of the neutralized rust which has been partially converted. Technically speaking, phosphoric acid isn't as much dissolving the rust as it is converting it. It causes a reaction and turns iron oxide (the rust) into iron phosphate which is very hard and stable and reduces the chance of further rust forming.The dreaded white residue is a crystalline structure that bonds to the metal, the good news is that it also inhibits rust from forming again, the bad news is that paint doesn't like to stick to it. The residue often appears when either the phosphoric acid is rinsed with water before it has completely converted all of the iron oxide to iron phosphate and exposure to air causes the very hard crystal structure to form and molecularly bond to the metal, or it can also happen if the phosphoric acid solution evaporates before all of the iron oxide has been converted.There are a couple of solutions to get rid of the white residue: 1) if it is appearing within minutes or a few hours of applying the phosphoric acid solution, you can typically apply more of the solution (make sure it stays wet with the solution) and it will dissolve the white while continuing to convert the remaining iron oxide to iron phosphate. 2) if the white crystal residue has been on the surface for days or weeks, then the best solution is removing it mechanically (e.g. wire wheel, steel wool, wire brush, flap disc, etc.), which will remove it but you will be exposing the raw metal again and it will likely flash rust within a day or two if there is any humidity in the air so be prepared to coat it with something (yes, more phosphoric acid solution/Krud Cutter will work and once all of the iron oxide is gone and the surface has remained wet with the phosphoric acid solution, the white _should_ not come back. YMMV, but I have used this many, many times on 20 to 30-year old rust with no trouble. Just keep it wet with the solution until all of the rust is gone.