Strippers

Any restoration project will inevitably confront problems with stripping off old paint and removing rust. A variety of methods are available, and no one of them is universally suitable for original or modern finishes, steel, aluminium or plastic surfaces or even considering the physical aspects of the area and its accessibility. What follows is an overview of strippers. I've found it useful to consider paint and rust removal methods in four broad categories: Chemical, Mechanical, "Sand" Blasting and Rust treatments and preventatives. Each has its attractions, and no one is universally "best" or preferred.

Chemical paint strippers are ideal for the Austin Healey's aluminium shrouds, and are a good choice more generally. These are specialized chemical concoctions that will be the main focus of the discussion here. These chemicals soften the paint and allow it to be scrapped off with either plastic scrappers (for aluminum) or metal ones (for steel). The chemicals are an effective methods for stripping large areas and areas with limited access or clearance for other tools. The chemicals are applied, allowed some time to take effect, and then scrapped off. Caveats:

I personally prefer these chemicals to the other methods, they may be messy and smelly but they do the job reasonably well and with rather less effort on the whole. I've found these particularly useful for those inaccessible nooks and crannies that wire brushes cannot reach.

Safety Advisory: (This hint is due to my wife, a former nurse with extensive professional experience of rubber gloves and obnoxious chemicals/people)

Anyone using chemicals for paint or rust stripping should use gloves to protect their hands (and goggles for your eyes). The chemicals will, sooner or later, eat latex gloves. When this happens you will find the nasty, horrible chemicals you'd been avoiding are suddenly unavoidable. The simple solution is to wear two pairs of glove á la Doctor Kildare and AIDS- the outer glove can be contaminated and used until it rots to pieces, then it may be easily removed, the underlying glove cleaned if necessary and a new outer glove put on. The whole point of using the gloves is to keep your hands clean, and another pair used for inner ones, whilst chemically dissolving several pairs used as outer ones is no big deal. Its neat and it works. And its probably the only thing my wife has happily contributed to the Healey....

If you look very closely you'll be able to see the less white looking inner glove coming higher up my wrist than the outer glove- that "gap" makes it easier to get only the outer one off- leaving your wrist clean and not smudging paint or chemicals on it from the dirty outer glove on the other hand.

Two of the more popular chemical strippers available in the UK. The Nitromors is the leading "Brand-Name" product. The "Homebase" is one of the alternatives- a "house" brand supplied by a chain of DIY/ Hardware stores. They seem to be the same product: they look the same, have the same consistency, smell (taste?) and apparently work equally well, etc. The "house" brand is cheaper.

Pour what you need into a suitable container, and brush on the surfaces to be cleaned, preferably using a disposable brush and certainly using one that you're not going to use later to apply paint. The active chemical ingredients in both are Dichloromethane & Methanol. How much you need will depend on how many coats of paint and primer need to be stripped, and how strongly they stick to whatever you want clean.

Note too that more common and cheaper paint stripping chemicals such as turpentine, white spirit, lacquer thinner/acetone etc. may be used. I've generally found these to be much less effective (i.e., not worth bothering with at all) than the special chemical formulations described above. The differences are substantial, though the processes used are usually the same. These other chemicals ARE useful for de-greasing and generally cleaning parts that have oil-impregnated and encrusted dirt on them.

If you have sizeable areas to strip these chemicals are ideal. For smaller areas they'll work just as well, but you may end up with a lot of unused stripper.

Final NOTE: BEFORE using any of these chemicals its a good idea to use a scrapper to remove any built up grease or road grime from the surfaces to be cleaned. This is much, much faster, and saves the chemicals for removing the stuff its designed to remove. I've also found that scratching the surface of the paint slightly also seems to give the chemicals a point of attack to help them work. Just don't be too enthusiastic else your panels will need rather more "bodywork" later than before.

The traditional wire brushes can be very effective in some applications, particularly where relatively small areas need to be cleaned, or where the area is relatively flat. These are good for areas with relatively light rust too so that chemical strippers would only deal with part of the problem. They are abrasive and remove paint and body filler with a degree of physical aggression. These abrasive methods may also damage any underlying surfaces. It is advisable then not to use such tools on the aluminium shrouds, thin materials or anything else likely to be damaged by abrasion.

The hand brush (and hand scrapper) is only really useful for light cleaning. Removing dirt, grease and road grime from components that will then be more thoroughly cleaned with other solvents or tools. A good scrapper and hand brush can very quickly and easily remove much of the surface dirt and grease before the more powerful tools are used. They're inadequate for rust and paint removal generally but clear the way for those that are. The kitchen knife is an indespensible tool useful for many jobs, this one was bought specially for the garage and not stolen from the kitchen drawer...in fact, my wife's a little annoyed that I have a better knife in the garage than she has in the kitchen.....

I've found a variety of wire brushes to be useful. The broad, flat ones (shown in the leftmost picture below) that mount in an electric hand drill are very useful for removing light paint and rust from small areas. Or larger areas, if necessary. These brushes are unsuitable for tight areas- they're just too big to get into all the nooks and crannies. To reach into these areas there are wire brushes of a "cup" design and "end" brushes. These allow the brush to get very close to the sides and corners of areas to be cleaned. Nevertheless, they may still be too big to reach the areas that need cleaning. In those cases the ultimate solution are brushes for "Dremel" type tools. These have very small shafts (6 mm) and come with flat, cup and end type brushes. With these its possible to reach into almost any area that needs cleaning.

Standard & small

Cup & End

"Dremel" - very small

The wire brushes are quite effective on paint, but rust resists their effects more. If there are significant areas of rust to clear then more aggressive mechanical methods may be necessary.

Effectiveness on Paint 5

Effectiveness on Rust: 3

+ Relatively cheap & uses drill

- Throws wires out

Composition Type Stripping Wheels- Drills

A "double" width wheel on the left, a standard single width one to the right.

The unusual texture may be easily seen.

A badly worn composition wheel- edges and roughness will destroy it.

These wheels are made of a mystery material. It looks like some type of heavy plastic that had been blown full of little holes and dried. A very porous grinding wheel that may be mounted in a hand drill and used to abrade any unwanted paint from most surfaces. I've used these on aluminium carefully with light pressure and seen no visible ill effect (as a test- on the back of a panel, but chemicals are much preferred for that material). These are more aggressive than the simple wire wheels and clean areas more quickly. These wheels can be found in a standard width of about 1/2 inch and a double wheel of two disks on a single shaft with a width of about an inch. These cost more than the wire wheels, and will wear down more quickly, but they do a much more effective job on removing paint, and work fairly well on rust too.

Effectiveness on Paint 7

Effectiveness on Rust: 5

+ Effective & uses drill

- More expensive, leaves "bits" as the wheel wears away.

- These wheels are great for smooth surfaces BUT edges and protrusion can tear them apart.

These wheels are made of numerous flaps of what appears to be sandpaper. I've used these some but they are a little unwieldy and do not seem to be quite as effective as the other abrasive wheels available. They seem to be about as effective as standard wire wheels.

Cup Type

Wheel Type

Drill Type

These are not as robust as the angle grinder types,

as shown in the photo on the right.

These wheels are the ultimate mechanical method for removing paint and rust. The wheel consists of numerous bunches of thick wires all twisted tightly together. This provides a more rigid abrasive set of wire ends that attack the materials to be removed. Where standard wire brushes might take several seconds to show an impact these brushes rip the paint or rust off and hunger for more. These are available in both a wheel and in cup configurations for angle grinders. I've not seen any available for drills, but the angle grinder is more suitable for driving these- they are dangerous and an angle grinder provides better grip (use both hands, please- and never tell your personal injury lawyer that either hand let go for an instant) and control than a drill would. Note too that the "wheel" one shown in the picture has been very heavily used and the "twist" has gone out of its tufts. But it will still rip paint and rust off better than the others. The drill type wheels are useful but only for light duty applications. The wheel type for the drill was badly distorted under heavy load. The cup type for the drill seemed better designed/assembled and were more effective. The angle grinder models are the much more effective and well worth their cost, the drill types are expensive given their short working life....

Effectiveness on Paint: 9 (angle grinder type only)

Effectiveness on Rust: 8

Effectiveness on Skin, Flesh and Blood: 10+

(Eminently suitable for any master criminal seeking a new identity, these will remove every trace of your former appearance very, very quickly - little effort and no attention required- just drop it with the run "lock" on)

+ Effective, unbelievable by comparison to standard wire wheels.

- Expensive and needs angle grinder.

- Dangerous!

-- Completely unsuitable for any "soft" materials- plastic, wood (flesh), most notably the aluminium shrouds.

Also known as "sand" blasting. Though it shouldn't be. Sand is dangerous, using it can lead to health problems and respiratory illness. Avoid it. The chief alternatives are oxide, slag and beads. More exotic possibilities may be used too- things such as baking soda and ground walnut shells have been used for delicate items. Each is available in a variety of grades- very coarse, coarse (60 grit) to fine (120). I've found it useful to start with a coarse grit and work on those items that require heavily cleaning, and then re-use the grit as it wears down for the less demanding applications.

The most important element in any system is the air compressor- it powers everything else and your ability to work will be helped or hindered by it. When its good, it will be taken for granted, and when its not up to the job it will be both frustrating and annoying.

The two compressors shown are almost adequate for media blasting. They are both driven by 3 horsepower motors coupled to compressors rated at 14 CFM (9 CFM free). They're pretty capable for most jobs but media blasting requires a lot of air. These just about manage, but the next step up to a higher capacity compressor and larger tank would have been much more expensive, would have required too much room in an already tightly packed work area and simply would not have been required often enough to make those sacrifices worthwhile: and the larger models would require heavier wiring than is usual.

If there are few items to be blasted, or if they are small, then these would both be more than adequate. But if there are large numbers of items, bulky and heavily rusted these then would be a little strained by the effort. I've found that they cope- but the compressors run too much, and the pressure can fall to the point where it is less effective. Nevertheless, the compressors can provide a useful enough output to do the job. The larger tank is useful for it allows a longer period during which the higher pressures may be used. For heavily rusted items this is important, for smaller items or those with less demanding cleaning requirements it is not so useful.

A belt-driven compressor with a 50 liter tank

The belt driven compressor is significantly quieter. I found that a distinct advantage when I spent hours blasting away at heavily rusted suspension components.

If I had the space and the money it would have been attractive to have a 5 horsepower 21 or 30 CFM compressor with a 200 liter tank- but then I'd hardly use it. I'm using the compressor for blasting intensively for a month, after that the equipment would be used for paint spraying fairly intensively over a short time and then once the car is complete the equipment would be used only occasionally.

If I had to do it all again I'd figure out some way to use the output from both compressors to drive the system- I'd borrowed one for a while and then bought one for myself. A bigger one wasn't economically attractive though it would have been most useful for blasting. Under the circumstances, my own and borrowed middling sized compressors would jointly work pretty well I think.... (Update, 7/2004: I'm now running two belt-driven 3 HP compressors giving a combined output of ~28 CFM and these work so much better than one- this combination is slightly cheaper than a single large compressor, and when I'm done I can sell one)

Blast Guns

A typical blasting gun, with a canister holding a liter of grit. These are relatively cheap and effective and are useful for small amounts of blasting. There are drawbacks to using these for larger projects- the canisters only last about 10 minutes for more-or-less constant use. This can be a blessing for it lets the compressor catch up or rest. But it makes for poor productivity when dealing with numerous items and particularly for those that are very rusted and need a lot of cleaning. A further problem is that holding the gun with a canister of grit becomes very tiring- the grit is heavy and will soon wear the user down. The gun too sprays the grit everywhere. The advantage this gun has is its more effective use of the air provided- it doesn't have to suck grit from a distant supply. The rated air supply for this is 8 CFM, and either compressor coped with it reasonably, for short intervals.

A "spot" blasting gun, the canister holds the grit, the bag at the front catches the used grit, and various rubber nozzles allow it to concentrate on cleaning just small areas. This is basically the same as the gun above but designed for smaller jobs and to do them more neatly. The nozzles allow spots of roughly 1/2 inch diameter to be blasted, and for inside and outside corners the concentration of grit makes for a neater job. The cloth pouch also keeps the grit from being sprayed everywhere. This is probably the best solution for dealing with a few rust spots or limited areas that need cleaning. This too requires 8 CFM, but its not required for very long given that the gun is held directly against a very small area to be cleaned. I suspect that a smaller compressor would be able to manage given sufficient pressure in its tank.

A bulk feed system-

ideal for big jobs

This is the ideal solution for large jobs involving numerous items with varied cleaning requirements. The gun itself is light- the canister has been removed and the grit is feed through a hose and tube "feeder" that may be some distance away. This makes the gun much lighter and lessens fatigue, and it allows a much larger volume of grit to be employed so that the user need not stop to refill a small canister. The one real drawback I see to this system is potential loss of pressure that sucking the grit several feet requires- the effectiveness of the blast stream must be reduced. I've also noted that the feeder hose is liable to blockages- probably because I'm reusing the grit and its not so clean or dry. But this seems a small loss compared to being able to work almost constantly without have to pause to refill canisters. This system requires 10 CFM, and the individual compressors almost coped... hence the real motivation for moving to a system using two.

The "bucket" full of grit- this allows for far better use of the time devoted to blasting parts clean. The hose needs to be kept out of the way, and the nozzle that goes in the bucket needs to be positioned to ensure a smooth supply of grit. The bucket shown was fine for holding a lot of grit, but it was so wide that not all the grit would slide down to the nozzle's intake. I had to kick the bucket every few minutes to ensure a continuous supply. A minor irritation- less trouble than re-filling a canister and one that I could have remedied by spending money on a proper supply container. I've also found that with some types of grit that the nozzle develops a static charge and can give a shock.

Ideal candidates for media blast cleaning. These small parts won't take much blasting and the inaccessible corners and folds make it virtually impossible to properly clean them in any other way.

Other candidates not shown are the heavy suspension components that are susceptible to rust- the wishbone arms, anti-sway bar brackets, springs, spring pans, seat frames etc.

On the whole I found it most effective to use the knoted wire wheels to mechanically remove most of the rust, and then use the media blasting for the final finish and those areas that the wheels could not reach.

Heavy Gloves certainly- even the large items would shift when hit with grit and air at 100+ PSI.

Face masks or goggles are needed to protect your eyes from the grit. Some type of breathing mask is highly advisable too, as well as a cap to keep the grit out of your hair. The dust will go everywhere and get into everything so a thorough cleaning after it all is necessary too.

The ideal solution is a small sand blasting cabinet to isolate the items being stripped and the blast grit. I built my own, but commercial ones are readily available.

Blasting Effectiveness

Once I'd settled on a bulk feed system feed by two 3 HP compressors delivering 28 CFM I ound that the system worked extremely well. The bulk feed system allowed me to work more or less continuously, and the two compressors jointly had the capability of providing enough air flow to make waiting for the holding tank to fill unnecessary- I had close enough to full pressure almost full time.

The blast gun used nozzles and these did wear out, as may be seen above. A check on them every hour or two kept everything working properly. The media used was re-cycled, despite being "disposable" . Thus I found it sensible to start with the most heavily rusted items first, so that the "fresh" grit that was most effective could be used on them. The less corroded items were left to last when the finer grit smoothed from earlier usage was used.

The sand blasting was extremely effective. Shown below are before, during and after photos of the blasting of heavily rusted motor mounts. These were ideal candidates for blasting for they had a lot of rust and their shape made other methods unworkable. A few minutes was all it took to take the mounts seen in the before photo and strip the rust completely from them as seen in the after photo. I found that a small sand blasting cabinet was a great assistance for stripping and re-finishing many of the parts required.

Before

During

After

Two types of rust converters are commonly available. Both employ chemical reactions to neutralize the rust. The first type uses chemistry to remove the rust and employ a mild acid that reacts with the rust, removing it and leaving a surface in which the iron has reacted with a phosphoric acid to yield a rust resistant compound. In this process the rust is removed- dissolved in acid- and all the metal is protected. The second type converts the rust from an active form into an inactive one. The rust is normally a ferrous oxide compound that consists of a single molecule of iron combined with two of oxygen. This oxide is unstable and seeks to combine with more iron, so the rust may then propagate and infect other iron molecules to form oxides with them too. The other converter leaves the rust in place but converts it to a stable form, one that does not further propagate. This approach stops the rust and protects it from further oxidation, but does nothing to protect unaffected areas.

Kurust is a Hammerite product and is one of the more well known and respected products. It has performed well in practical tests undertaken by a British magazine. As I understand it Kurust converts the rust from an active form into an inactive one. This approach stops the rust and protects it from further oxidation, but does not protect unaffected areas that must then be painted for protection.

I used Kurust inside the outriggers and other internal areas where I could be sure of coverage, and will then apply a liberal coating of Waxoyl to prevent future difficulties.

Metal-Ready is a POR-15 product and is part of their paint system. The idea is to remove most loose rust, treat the surface with Metal-Ready to remove any corrosion and then over-paint with POR-15 paints as a primer for a finish coat. While POR-15 is advertized as being applicable over rust and will bond with it to prevent any further corrosion I thought a sounder approach would be to eliminate the rust first.

I used Metal-Ready on all " small parts" to remove any corrosion and to prepare those surfaces for priming with POR-15. The chassis and inner body panels were to have been treated, but I've decided to have them sand-blasted instead and then have the POR-15 primer sprayed on.

Waxoyl is produced by Hammerite. It too is one of the well established and respected products used to control rust. Liberal amounts are to be injected into most sections of the chassis- if the section is open to air it is then fair game for rust and invites a dousing with Waxoyl. The Waxoyl will be warmed to improve its viscosity and spray-ability, and a spray gun with an extended wand will be used to treat the rails, and other areas.

Dinitrol is an alternative to Waxoyl. There are different formulations available for different applications. One (not shown- Dinitrol 3125) seems pretty similar to Waxoyl But another (the one shown- Dinitrol 3654) seems to perform somewhat better that Waxoyl in that it is "thinner" and can get into areas that Waxoyl cannot. Better for seams and the like where protection between panels is needed. I haven't yet used any but anticipate doing so and will report on my experiences here in due course. Also shown is a tube of the Dinitrol seam sealer.

Dinitrol applied to the Jensen Healey rear inner wing. The panel was thoroughly checked and cleaned. Then I first applied the 3654 formulation as it's supposed to penetrate more effectively; then the heavier XXXX formulation was applied to seal and protect the surfaces. This provides a shiny black protective coating that would give good protection against stone chips and water. I warmed the goo first by setting it for a 1/2 hour or so in boiled water, with heated water added every few minutes to get it hot. I had thought about setting the cans in a pan or "steaming" them but good sense for once took over and a plastic bowl on the kitchen counter sufficed.