Prepping: Derusting & Refinishing

There are many joys of working with your hands…the pride of bringing something back to life being foremost among them.

Unfortunately, there are many problems with “restoring” and “refinishing’ so we thought it would be useful to pass-along some of our lesser-known tricks.

Let’s begin with paint:  It can be miserable stuff to remove.  However, there’s a dandy product that removes paint like crazy, although from metal, not wood:  Rust-Oleum 255449 Aircraft Remover, 18 Oz Aerosol, Liquid, 18-Ounce, Clear.  Goes for $11-bucks a can at the ‘Zon.

This is mean, terrible, nasty stuff.  When applying it, make certain you have on skin and eye protection.  Don’t use when windy because the last thing you want is a trip to the hospital from breathing some in.  That said – along with stand in a neighboring county while spraying if possible – this is a GREAT product.  Spray on, wait 10-15 minutes, and then blast with a pressure washer.  Drive-through bays at a car was are ideal.

If you don’t have any remover handy, the second most-favored tool around here is a “needle scaler.”  It’s actually a small (noisy!) air tool that requires a reasonable compressor to run.  But, if you have that (and $47 bucks to spend), I’ve been using a Sunex SX246 Pistol Grip Needle Scaler for about 6-months now and it does a reasonable job of removing crap from metal.

What we have here is Mr. Ure’s refinishing of the cabinet for my Johnson Pacemaker Transmitter, which is the matching exciter for the Johnson  linear amplifier.

Using a needle scaler is not terribly difficult:  What you do is glove-up and cover the eyes, and yes, you wear a mask just in case although the operation is not particularly dusty.

The tool is held at a 30-60 degree angle from vertical.  This is NOT a tool to use on aluminum, however.  Since the kind of dieselpunk vintage radio gear I work on (tubes) was built before “value-engineering” became the rage, this radio has a steel cabinet that is not too difficult to clean up and make “purdy.”

One glitch with this one is that it was seriously damaged in shipping (the seller and I are dancing with FedEx about this) so there’s one ding on a corner that I haven’t decided how to repair.  One choice (Bondo) is easy to fill in, but the other (quick lay-up of filler rod with a torch, then hammering and grinding) is a little more risky and gets deeper into auto-body skills than I’d planned for this project.

This gets us to the next consideration:  Which metal primer do you use?

Most (shade tree) mechanics wrongly believe that “primer is prime is primer…:”  Nothing could be further from the truth.

When you’re going for a workman-like job, you need to understand that there is Shop Primer and there is Finish Primer.

Shop Primers are not especially tough.  The term ‘shop primer” means that it can be just enough to keep material from beginning to degrade prior to (on the assembly line model) moving on to the next “shop operation.”

Finishing primers are more aggressive.  These include etchants which ensures that the primer will cling like mad to the metal and, when the finish is applied, it will bond giving you a really nice finish.

For a lot of the radio gear I enjoy working on (old Hallicrafters, Johnson, and Drake gear) it’s fairly simple to come up with correct paint on eBay.

ideally, of course, we would put on a solid powder coat and bake until properly toughened.  But, it would be a bear to get the powder coating ready and con Elaine into going shopping and give me enough time to use the oven (plus air the house out afterwards), so I stick with the paint!  (See? Laziness and long marriages are compatible!)

The other thing to look for in your “etching primer” is the amount of build up that it provides.  I use SEM 42013 Grey High Build Primer – 16 oz.which, while not cheap (just north of $21) provides a good build-up for covering minor imperfections such as might come from grinding or sanding with something less than fine wet-or-dry paper.

This may seem like an absurd number of brain cells to toss at something as “simple” as making an “old radio work.”  But, it’s little-different than the mindset of the chassis-off auto restoration crowd.  We just have more wires to play with.  And none of the POR-15 rust-preventing chassis coatings.

Since Elaine and I don’t have kids coming around this weekend, we will be doing projects.  While it seems like we have “too much of everything” tool-wise, when comes to being able to turn out good work in a reasonable amount of time,. there’s nothing like the “right tool.”

Humans, being tool apes at heart, take no end of delight in turning everything in sight into a tool.

A while back, I was cutting up cardboard boxes with a reader comment sparked me to get an old “hand wipes” contain and load it up with pieces of cardboard like these…

The reason is simple:

How many times have you needed to start a screw or a nail and you just couldn’t get the tool and the fingers to occupy the same space without injury?

This little guys are so easy…take seconds to make by the thousands – and they are small enough to be picked up by the shop vac.

When you’re using these, if you put the nail right up into the groove, you can get them to be dead square which is something close to impossible to accomplish without a guide of some kind.

I have a pet theory that smashed fingers (which accompany using too much phone and not enough real tools) accounts for the huge growth in power screwdrivers.  Truth is, with enough charged batteries, we could probably disassemble half of our home for shipping, lol…

Oh yeah – one late entry for Santa:  If you don’t have a set of ‘quick change drills” they are THE most-used new item at the workbench for all of 2018.

For most “light home shop” applications, a set of these will generally get you into the “close-enough to work” range.  A Bosch 9-Piece Impact Tough Titanium Drill Bit Set, TI9IM set will nail you for $14-bucks and it’s tooltally )sic) worth it…

Off to play…moron the morrow…

19 thoughts on “Prepping: Derusting & Refinishing”

  1. my forte was landing gear overhaul. the bead blaster and zinc chromate made for easy work. thanks for the great article, off to play as well…metal storage cabinet refinishing,lol! happy holidays.

  2. George

    I am in the process of restoring a 38 year old Heathkit oscilloscope. I took it apart into it’s major sub assemblies. I found that the interior steel chassis had become spotted with light rust specs from the southern weather I live in. So I decided to clean and paint it. I left the wiring harness attached to the chassis as removing it would probably destroy it. So that left out any kind of sand blasting or other heavy manual cleaning.

    After some research I found a chemical Rust Reformer that Rust-Oleum makes. I used it and had good results. It goes on a bit thicker than I preferred, but I did want to kill the rust.

    At this point I was left with the question of what paint to use. As I had left the wiring harness in place I decided to hand paint it with a brush.
    Not the best choice. I had wrapped the harness with plastic as best I could but I was still concerned that spray painting would get onto the wires. So I found an oil based gray paint also made by Rust-Oleum.

    At this point I made the mistake of not thinning the paint. After painting about half of the chassis I decided I just could not get rid of brush strokes. I went on line and did more research and found I could cut the paint with acetone. This I did and thinned it by 50%. It was much easier to apply the paint to the nooks and crannies of the chassis without brush strokes being left on the surface.

    It’s not the Mona Lisa but it’s usable and as it’s inside the scope nobody will see it. Next time I will commission my son the professional painter to do the job. He owes me for a few thousand favors!

    • I try not to do chassis paint, although there is a hallicrafters ham and gen coverage receive circa the art deco period that has an all gray interior…my thing is dieselpunk ssb radio gear.
      Point is, make sure that you don’t screw up any chassis grounding with paint. One can be impressed with some of the older gear by just refreshing the grounds (wiggle, twist, retighten all ground lugs) and replace all the electrolytic caps in the supply – they dry out over time and tend to short closed which kills transformers in older gear…

      • Thanks!!

        Already thought of that and it is indeed important!

        All grounding is now going to be routed to a single point ground terminal board. A line filter will also be installed on the incoming AC power.

        The high voltage paper and electrolytic caps in the power supply are scheduled to be replaced.

        Many out of tolerance resistors and transistors have already been replaced.

        Much work still needs to be done but that keeps me off the streets and the public safe!

        Merry Christmas to You and Yours !!!!!

    • Rustoleum Rust Reformer! That’s the ticket I was looking for to start the fix on my rocker panels. Thanks!

  3. Great info! Other than a plane with weight and balance considerations, or horribly flaky paint, I can’t see using the A/C stripper for most things. It’s good to know though. BTW, acetone does a fair job on most paints. On the drills, I don’t have the “quick change ones. I prefer a step drill permanently chucked in one 1/2” drill(until it finally breaks), since step drills have more mass to prevent breaking, and they can work even in thicker steel than the step. The hand tightening chucks are almost as fast as the quick changers, and small drills will break easily, so I have lots of them.

    I’m no chassis changer unless it was for something truly special(I have one project where I might double another chassis under a nice class B RV), but knowing something that could stop rust in its tracks on rocker panels would be useful. Even here in the mountain west, those things rust if you wait long enough. Auto body work is not my forte – and it’s more about getting it done than perfection.

    Just my tuppence!

  4. “This is mean, terrible, nasty stuff. ”

    Funny you should bring up paint.. A couple days ago I got a call from one of my siblings. His hobby is restoring old rare cars..he could probably open a museum but once in a while he’ll sell one..
    He called to see if any of the results was in on the biopsy of some of the tumors I have. ( not yet they had to be sent off..) anyway he brought up the possibilities of my exposure to chemicals.. I’ve had a lot of hats and back in the day gloves or masks wasn’t on the list..then he talked about my painting cars and doing air brushing pinstriping etc. And this class he took on car restoration. He said the first thing that was brought up was cleanup.. How many times have you had paint grease etc. Where to get it off you just doused yourself with thinner or gasoline and did a quick wash .. Or trichlor etc. Cuts right through then soap and water.. Well they showed them just how dangerous it was and how many seconds it took to start attacking the kidneys and liver from getting it on your hands..shoot a week ago I did a quick rinse for grease.. Lol I guess I never gave it a second thought. He was saying most of the finishes today are so dangerous that he wears bio suit with fresh air breathers..

    • This tends to prove the old rule that the more toxic the chemicals, the better the possible result! Sad but true.

      • Amen….mike trust me I’m paying for it.. Back in the day gloves were unheard of so were masks.. Actually never gave any of it a thought..I was to busy trying to support a family..

    • I admire ‘handy men’ and ‘handy women,’ but you can keep the industrial toxins you are exposing yourself to…..paint, varnish, grease, paint thinners, you name it, it is highly toxic. The aerosol versions are a triple whammy.

      • Ray:
        Carbon Tetrachloride, strong stuff. You may remember it was sold as a spot remover for clothing, which led to the joke-
        I used spot remover on my dog, and now he’s gone!

  5. Considering the dangers of chemical contaminants..That brings to mind the new fad..
    Vaping….instead of smoking..
    The grand daughter asked my opinion.. Which is worse..
    Smoking..tars, nicotine ( a poison) benzine a product we use to use with oil to loosen rusty nuts.. Now its only used by the oil industry and tobacco industry..
    Vaping ..basically a hot vaporizer.. But the solution is basically antifreeze and vegetable glycerine ( for the clouds of steam..same thing you mix to make huge bubble solution for the kids) and nicotine..
    Plain distilled water would be healthier but both are dangerous in my opinion.. Which is worse Smoking in my opinion if I had to use either I would pick vaping.

  6. Stopping rust and reforming it to Iron Phosphate black ceramic… is a product called
    “OSPHO”… phosphoric acid solution. Brush off the loose rust scale, Ospho it and let dry for a day, and you can paint over a black ceramic layer that will not rust further.

  7. I am not thrilled with powder coat finish. it’s basically plastic melted on the metal. There is no primer, and with any exposure to weather, it rusts and the rust creeps under the plastic. My dump trailer is a mess, but looked great when new. Lawn carts, vehicle bumpers, are all a mess from rusting under the plastic.
    If it’s going in a indoor display case, maybe powder coat is OK, but I’m pretty sure I’ll continue to avoid it when possible

  8. Check out Eastwood Automotive, Malvern,Pa. As a retired refinisher/restorer myself,this was our sears Xmas catalog. Happy holidays !

  9. Essay time, and I apologize in advance. Restorers and DIY-types will find this useful, others, not so much…

    The principal rust removal agents are sulfuric and hydrochloric acids. Get a quality gun rebluing kit and it’ll probably contain both, along with nitric (for “nitriding…”) and phosphoric acids. I use HCl for ferrous metals, and sulfuric, in combination, for rust that’s coming through a nonferrous coating, like the purty copper plating radio mfgrs. used on their high-end chassis.

    Phosphoric acid is the standard for “rust conversion coatings.” Ferrous metals treated with phosphoric acid are slightly etched, and acquire a thin layer of ferric phosphate on the etched surface; rusty ferrous metal so-treated has its rust “converted” to a more porous or spongy ferric phosphate, which may not reach down to the base metal. Ferric phosphate is immune to oxidation.

    Etching primers have the titanium dioxide base found in most paints today, and contain chemicals which form phosphoric acid, but not until they are combined in free air. Phosphoric acid makes an excellent “paint prep” because its etching action leaves a “treebark-like” etched substrate for paint or primer.

    Rustoleum Rust Reformer uses carbonic acid in a vinyl base instead of phosphoric acid in titanium dioxide. I’ve no experience with carbonic rust killers because what I use is sufficient to the task…

    Every stripper I’ve ever seen is some formulation or other of methylene chloride — evil stuff. It dissolves flesh as readily as it loosens & dissolves paint. I’ve always used canned (brush-on) strippers, because I cringe at the very thought of breathing this nasty crap.

    My secrets:

    I’ve got several 14pc sets of Montana quick-change “titanium” drills. I even carry one of ’em in my electronics toolbox. They’re not a replacement for my CL cobalt set, but more than adequate for wood/nonferrous, and they’re quick to use.

    “The Works” toilet bowl cleaner, original (thin, watery) formula. It is 33% hydrochloric acid and optimized to eat rust. Ferrous metal bathed in this TBC will come out clean, shiny iron or steel, already prepped for primer, usually in 10 minutes or less (for thick or heavy rust, brushing with an old toothbrush helps immensely.) After treatment I wash parts in hot soda water, then hot dishwashing liquid water, hot rinse and towel dry, then prime immediately with an etching primer. Truly clean iron or steel will begin to surface-rust within 2-3 minutes, anywhere more-humid than the Mojave.

    For ferrous metal which doesn’t need to be “foundry-new” in appearance, I use Rust-Mort. This is a SEM professional product, used by auto body & paint types. I use it because when I was doing such, I bought it by the case (6 qts, $23, I dare you to price it now…), and after 40+ years, still have a bunch of sealed quart bottles of it. It’s still, just phosphoric acid…

    I pretty much always use etching primer now. Two double coats 10 minutes apart. It lays really well and requires a minimum of wet-sanding. It also allows paint to stick to aluminum without major headaches.

    I’ve started using Rustoleum (or Valspar, when I can get it) implement/industrial alkyd (oil-based) enamel as a ground coat on vehicles (and implements, and a couple radio towers.) It’s cheap, and very high quality. Cut 25%-40% with a medium reducer, and WITH HARDENER ADDED, it goes on smooth, is slightly flexible, sticks better than epoxy, and dries as hard as Imron did. Block sand at two days, paint or base/clear after 30 days, and the offending part will never lose paint or grow rust. With hardener added, it only has about a half-hour working time, so I mix it a cup or spraygun at a time. BTW sanding at two days is easily workable. Sanding at 20 days is like sanding a braze. When this stuff gets hard, it gets really hard…

    Ammonium chloride and a little corundum (aluminum oxide) dust make an excellent non-ferrous metals cleaner. Copper and aluminum load-up abrasives quickly, and the use of sandpaper to clean wires can deposit silicon into the wire, creating, in-effect, a semiconductor. I hate aluminum wire, but do sometimes use aluminum angle and sheet for faceplates…

    For really high-quality copper wire connections, I have a jar of Cool-Amp. This is a “cold” silver plating compound. A daub of it on a cloth, moistened, and one can permanently bond pure silver to any cupric alloy. BTW, it ain’t cheap. A 12oz can contains about 10oz of pure silver… Do the math!

    “Fixative” is something with which charcoal sketch artists are familiar. It is a thin, nitrocellulose lacquer that’s sprayed on with an atomizer and flashes dry within literally, a few seconds. ‘Don’t have an account at Dick Blick? No problem. It can be made by cutting clear butyrate dope 4x, or nail polish 7-8x, with acetone. Fixative will inhibit oxidation, and can be soldered through without issue.

    Speaking of nitrocellulose, I did mechanical, and an occasional body restoration on British sportscars in the ’70s. Upon considerable research, I concluded that aside from University Motors in the UK, there were exactly two sources for proper paint: Bill Hirsch and Stan Coleman. Hirsch was a Packard enthusiast, who couldn’t get paint for his pets, and so got together with some aircraft enamel folks and created, among other things, a line of extremely tough, high-temperature engine enamels. By the time I needed engine paint, Hirsch was producing both MG Maroon and Austin Healey Green, of which I ordered many a quart.

    Stan Coleman produced nitrocellulose lacquer, but also got in on the ground floor with cyanoacrylate-based paint (we now call this “urethane” BTW.) He and Hirsch both created a cyanoacrylate sealing & coating product which, although photochemically-reactive, would seal rusty metal permanently, hardened upon exposure to moisture, and would prevent any more rust from ever occurring. Somewhere in my car pile there’s a restored AMC 3rd member, coated in POR-15 and painted in black epoxy, which, after 34 years, is still rust-free.

    The stuff works, and is amazing, but [it] is not a cure-all. Read the applications sheet to determine if it’s “right” for the job, before sinking the bucks into it, and also understand, even with Saran Wrap stretched under the lid, the can is going to weld itself together, making its use more than about 30 days after initially opening the can, impossible. My first quart can cost $7.50, post-paid. That same can now costs >$47 at my local auto paint jobber…

    Rustoleum sells textured, and wrinkle-finish paints. I have used several of these for various restorations — ‘got a wrinkly Hallie? Use the Rustoleum to get texture, then paint over it with hot-rod gray primer, followed by Hallicrafters Blue (or light, or dark gray, although I’m thinking the only wrinkly one I have is an SX-20 in charcoal.) BTW “wrinkly paint” is a b!tch to get right. If you need this texture, plan on wasting several cans, and doing a LOT of test sprays, before you learn the technique which yields the effect you desire.

    Last, but not least, one can construct a simple plating rig out of a battery or PS, and a litter box. Use a copper fitting from yer local hardware store as an anode, anything from salt water to lemon juice as the solution, and that aforementioned copper-plated radio chassis can be replated in a couple hours, to fill the spots where the original plating went away and rust formed. Mask (if desired) the (now cleaned, formerly rusted) spots and spray the chassis with fixative. Peel the masks, and dunk it in the tank for a while. Either respray with fixative or strip it clean with lacquer thinner to then replate the whole unit as desired, and presto, like-new chassis!!

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