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| Phos-Kleen treated steel on the right, primer on the left |
I was once asked at a car show how I knew a certain product would protect against rust, I explained that the products had passed a 1000 hour salt test without failure ... "that's not long" the chap replied, "I want it to last years!"I then had to explain that the standard salt test cabinet represented an accelerated time period exposed to an aggressive atmosphere. I could tell he wasn't impressed but in a way he was right to be sceptical. I know of companies that claim wonderful things for their own products when compared to others on the market because of the results of their own salt tests. Comparable salt tests are only really relevant when each test is carried out at the same time on a piece of metal called a coupon, you purchase these coupons from approved test laboratory suppliers and they represent pieces of metal the same size and thickness from the same original batch of steel, so basically they all have exactly the same potential to rust. These coupons are coated to the sample submitting manufacturers specification and film thickness often by the manufacturer himself then submitted to the laboratory for comparable testing. This means they are all tested at the same time same day same conditions time of year etc. This is the only way you can actually get a subjective comparison of each products performance. I once sent away one of our products to a well know magazine for a comparison test our product came second it had the best corrosion resistance of all tested but in was scored down on price (never did understand that one) in an editorial statement in the following months magazine it had a paragraph stating that if it had been included in the test another product not tested would have been best in test, the manufacturer of said product claims to this day that his product had won the test, it may well be an excellent product but it wasn't at the same real time test carried out on that batch of coupons, so his claims are unfounded, whatever his own data says. Money talks I'm afraid when you can afford two full pages in a well known magazine. So if you don't see too many more of our products sent to magazines for editorial evaluation that will be the reason why. We have told them we will as long as the test is carried out on proper coupons at an independent laboratory. So like the chap at the beginning of this chapter there can be good reasons to be sceptical. At Rustbuster our products are developed in house but sent away to a government approved test facility for salt test evaluation. Any declaration of salt spray testing would indicate that the product has the ability to withstand an aggressive environment.
PAINTING TREATED STEEL
For vehicle under bodies suspension components floor pans and any treated steel a further coating of Rustbuster Epoxy-Mastic 121 will coat the steel in a completely impervious flexible iron hard barrier that will prevent the steel from future rust. This can either be left as a stand alone coating or it can be over coated with waxes sound deadeners, stone chip coatings or primers and topcoats. Car body work should be prepared back to clean steel treated with Rustbuster Phos-kleen B followed by a coat of Rustbuster Custom Epoxy 421 prior to body filler primers and topcoats. I have dedicated a separate section to car bodywork and the preparation and treatment of bodywork at the end of this section. Epoxy-Mastic 121 is the most effective barrier you can use in the structural parts of a vehicle. It's very small molecules are able to penetrate deep into the steels surface prior to cross linking (the joining of the A & B component on drying) this penetration is possible because of the low surface tension caused by these fine molecules. This surface penetration gives fantastic adhesion when dry due to it attaching itself to every pore, nook and cranny on the steels surface this kind of adhesion is called a primary bond. A primary bond is where every square millimetre coated is firmly attached. The use of single pack coatings and powder coating is often classed as a secondary bond, a secondary bond is like sticking two pieces of glass together they are impossible to pull apart, but as soon as a breach is made in the two surfaces they come apart easily, we have all seen powder coated steel where the powder coating falls off in sheets revealing the rust underneath, in my opinion you should save the powder coating for office furniture. Or single pack coatings where a rust spot leads to the rust tracking beneath the paint coating. The slow cure Epoxy in Rustbuster Epoxy-Mastic 121 ensures that the coating is completely bonded to the steel at every square millimetre in an extremely tough but flexible barrier coating. Even if the system is breached by a sharp stone flying at bullet like speed the stone chip will only corrode at that point, due to the primary bond it is not able to travel under the coating and cause de lamination. At a later inspection the rust spot can be treated and repaired with a touch up of Epoxy-Mastic. In my opinion you cannot do better. |
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Mustang structure coated in red Epoxy Mastic 121, including the chassis and floor pan. PAINTING OVER RUST AND CONVERTERS
To be able to paint surface rust there are a few precautions that need to be taken. After thorough degreasing all loose rust dirt and loose paint coatings still need to be removed, usually by Shave hook scraper or a stiff four row steel brush by hand. The awkward profiles of steel under a vehicle means that often preparation by hand tools is the preferred method. This will leave a fine layer of ginger rust that lies directly on the steels surface in fact it is the steels surface. This surface layer of iron oxide can be treated with a rust converter primer such as Rustbuster Fe-123 molecular rust converter. This converter actually uses natural substances bound in a latex film to physically change the nature of the steels surface from iron oxide to iron tannate. This can then be painted with Rustbuster Epoxy-Mastic 121. Or an under body wax. |
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The total removal purists may throw their hands up, but in my experience a large percentage of my customers want to treat rust this way so they might as well know how to do it properly. Remember we are talking about the steels actual surface which is iron oxide not any loose rust on top of this in layers, any loose rust left on the surface will compromise the adhesion of the paint coating, so all of the loose rust must be completely removed back to the steels iron oxide surface prior to conversion. Within crevices and seams it is impossible to remove all traces of rust without taking the whole assembly apart. In the case of crevices and seams it is vitally important that they are treated correctly. The seam needs to be cleaned of any dirt or old rust getting in as far as you can, the rust that forms within an oxygen starved seam or crevice will react instantly to humidity the rate of corrosion will be 400 times faster than surface corrosion. Inject Rustbuster Fe-123 or work in with a brush to ensure complete saturation of the rust within the seam. Fe-123 is damp compatible so even if there is damp hidden within the seam the Fe-123 will react using the damp to travel through to the steel. Leave the seal to dry completely and then apply SIKAFLEX 252 seam sealer as far into the seam as you can using the finest nozzle section on the cartridge. This can then be over painted with Epoxy mastic 121 to ensure a perfect air tight barrier. For hidden seams the Fe-123 will be applied via an injection gun and followed with a cavity wax. ( see wax section below) The key to successful painting of surface rust converted steel is in the barrier coat applied to the iron oxide surface that has been converted to iron tannate, as long as the steels surface is prevented from receiving air and moisture is cannot rust any further. Epoxy-Mastic 121is the most effective barrier you can use. Its very small molecules are able to penetrate deep into the steels surface prior to cross linking (the joining of the A & B component on drying) this penetration is possible because of the low surface tension caused by these fine molecules. This surface penetration gives fantastic adhesion when dry due to it attaching itself to every pore, nook and cranny on the steels surface. The slow cure Epoxy in it ensures that the coating is completely bonded to the steel at every square millimetre in an extremely tough but flexible barrier coating.
STRIPE COATING
Stripe coating is a method used in marine painting that I would recommend to all when coating steel on a vehicle. Every edge of steel or sharp profile has the greatest potential to rust, proof of this is rust breaking out on the return edge of a cars wheel arch, we have worked with manufacturers of cars as recently as 2009 and some of them still get this wrong. So why does it happen? When paint is applied to a panel of steel it flows and wets out to form an even layer, when the same layer thickness is applied to an edge, the paint shrinks as it dries, the solvents leave the coating and its film thickness reduces as a result. The paint either side of the edge pulls in opposite directions leaving the paint thickness at the edge of the steel a fraction of the thickness of the paint on the panel. To prevent this is simple, applying by brush a coat of paint applied directly to the steels edge and not the surrounding panel will load up the film thickness of this vulnerable area prior to spray coating. This can be done at the initial primer stage using a good non porous epoxy primer such as Rustbuster Custom Epoxy 421 on body work or Rustbuster Epoxy-Mastic 121 on the vehicle underside and floor pan. |
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Loading up the vulnerable edges prior to painting
Look at the fantastic job this restorer is doing by loading up all of the vulnerable areas first prior to a second full coat of Epoxy Mastic 121
SEAM SEALERS AND AHESIVES
Seam sealers and construction adhesives also play an important part in rust prevention. Use of a polyurethane construction adhesive such as SIKA 521uvwhen assembling bolt on body panels will reduce the amount of corrosion that can take place due to the differing potentials of the steel used in body panels, shell and chassis, it will also insulate the nut and bolt which will also be of a different potential. A great deal of care should be taken when bolting aluminium panels to a steel body to insulate them from each other using a construction adhesive. Seam sealers should be used wherever required over the treated and primed surface then painted if required. Steels of varying thickness have differing degrees of rust potential if you bolted a very thin piece of steel to a thick piece of steel the thinner piece will rust first, insulating the interface of these steels and its fasteners will reduce this form of corrosion.
RUST PREVENTION ON VEHICLE BODYWORK
Again its preparation but almost more important is the primer. Most of the readers of this chapter I presume are going to be keen amateur auto restoration engineers. For your topcoat paint products you will go with your preferred manufacturers products and colour, but try not to mix and match too much as this could cloud the issue if an inter-coat problem arises that you need to speak to the manufacturer about. If he finds out that you have not followed his recommendations on base coats top coats and lacquers it gives him an easy excuse to walk away. The following will be a good base and suitable for you to either finish the body work yourself or send off to your local body shop to finish. One thing that manufacturers of these body shop products will assume is that the job is going to be carried out in controlled body shop conditions, where the temperature and humidity are managed. Of course this is seldom the case with the amateur auto restorer he will be restoring over a period of months or years and in some cases even longer and this is where the corrosion problem can arise. Why? In the UK we tend to use primers that are designed for adhesion and easy sand. The positives to this are there ease of use and the ability for the amateur to get a reasonably good result with little experience. But any primer that is easily sand able is also likely to be porous and this is where the problem is. In controlled body shop conditions a porous primer is not going to be a problem as the moisture content of the air is managed. But in a home garage workshop the temperature and humidity is going to go up and down like a yo-yo. At certain times of the year usually the winter months the steel will be at that temperature which is called its dew point. You know when you pick up a piece of metal on a cold damp day and it just feels sweaty and wet. At any such times you just cannot or should not paint, the moisture is going to sit on the steel and destroy adhesion, maybe even sit as bubbles of water waiting to blister out on a hot day or at least reduce the gloss level of your finish. You can be guaranteed future corrosion problems if you continue to paint under these conditions. Moisture trapped within a porous breathable primer is going to cause rust, once painted over you have the perfect little rust cell just waiting to burst out. So what's the answer? Well, waiting for perfect weeks or months when the work can be carried out are not an option in a country that has difficulty forecasting weather twenty four hours in advance. But you will need to consider painting the bodywork when the temperature is guaranteed to be reasonably warm and dry. The answer is in sealing the prepared steel against humidity. Basically on a warm and dry day or in a warm dry garage, you would prepare DA/Flap wheel sand back to bare metal. Chemically prepare this bright clean steel with Rustbuster Phos-Kleen B spray a little onto the steel and wipe over the surface with a 3m grey scotchbrite abrasive followed by a wipe with a lint free cloth. When dry de nib with a p320 abrasive followed by a wipe with a tack rag prior to priming with Rustbuster Custom Epoxy 421. This could even be carried out a panel at a time. The benefits of using the epoxy primer are its better adhesion and most importantly its non porosity this non porous epoxy primer can be left in its primer state for the duration of the restoration so however many years it takes to finish your good preparation will always be preserved . Rustbuster Custom Epoxy 421 can be filled with bondo and body fillers and will accept other paint coatings and finish coats without a problem. Rustbuster Custom Epoxy 421 is not an easy sand, but then if it was it would be more porous. If you are really serious about rust prevention on a restoration project then start with an epoxy primer. A typical body system would be. 1. Remove any loose paint and rust back to sound clean metal with DA or flap wheel 2. Treat steel with Rustbuster Phos-Kleen B panel wipe 3. Prime with Rustbuster Custom Epoxy 421 4. Fill and prepare defects metal loaded filler 5. Further coat of Rustbuster Custom Epoxy 421 6. Finish with body paint of choice |
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RUST PREVENTING WAXES
All of the previous discussion on surface preparation applies when considering the use of rust preventing waxes. I have discussions with many customers over the phone via email or at the shows we attend about the abilities of certain waxes performance at preventing rust. So at the want of repeating myself and as the Irishman said "Not starting from here If I were you" I am going to assume you have started from one of the already mentioned rusty / rust free situations and you now have a suitably prepared surface that you want to protect with a rust proofing wax. But what about cavities you can't see or prepare? Should you use a converter injected into the cavities prior to wax injection? ... I have long pondered this one, some say do some say don't. Back in the days when we used to deal mainly with marine corrosion it was a standard practise to soak hidden rust with oil like products that penetrated the rust inside the cavity. And due to the barrier effect it worked to a degree.The rust that forms within a crevice or seam within a hidden cavity can corrode at up to 400 times faster than corrosion on open surfaces, once humidity enters the oxygen starved crevice this rate of corrosion is just about guaranteed the application of a hygroscopic converter to passify this rust and seal it in a laytex layer is something I prefer to do... Whatever way you choose to go I'll offer the pro's of using a rust converter within cavities and let you decide.
Rustbuster Fe-123 can be diluted to reduce its viscosity it is also damp compatible this means that it will still penetrate and convert when injected into hidden cavities even when moisture is present, in fact any moisture within the cavity will then carry the converter further into the seam by hydroscopic action. Now that's got to be a positive. Agreed you may well have loose rust on the surface of the hidden cavity but you are not looking for the adhesion of a surface coating within the cavity, just make sure to use plenty of it.
The delivery method for injecting cavities needs to be able to atomise the product sufficiently to allow it to penetrate. Rustbusters Pro-wax injection gun is a good solution to this. Once the rust converter has fully cured you can inject the cavities with a cavity wax. Rustbuster MIL-SPEC. ASTM cavity wax will spray direct from the can when applied to the vehicle underbody for cavities this universal solution should be thinned 25% with white spirit for perfect penetration. Rustbuster MIL-SPEC. ASTM cavity wax left next to a radiator or in the airing cupboard overnight will give you a superb penetrating wax even on the coldest winter day the extra thinning for cavities should be used for extra penetration into tight seams. During the summer months it is always at a spraying consistency. Pour the wax neat into the Pro-wax injection gun and off you go, pushing the probe fully into the cavity squeeze the trigge/strongr and draw it slowly back towards you. You can't really use too much if you do, it will be in a pool on the garage floor. Just make sure to coat every part of the cavity. That's why we use a wax that flows from the tin without thinning that can be atomised and sprayed into a cavity and sets up as it dries into a flexible waxy film. a hr/h3ef=This then forms the barrier protection against rust we have already discussed in previous paragraphs. By all means pay attention to the salt spray test that some manufacturers use as a selling point, it is definitely relevant when dealing with under body waxes. In my opinion the test that really is significant for cavity waxes is the humidity test this is an ASTM test requirement more than surpassed by MIL-SPEC. ASTM wax and was a significant for us choosing this formula, it also has excellent ASTM salt fog protection as well, so all in all, great penetration and protection and no thinning required so the high film thickness offers an effective barrier against rust. For the vehicle underside suspension components etc. Rustbuster MIL-SPEC. ASTM wax can be applied over Epoxy-Mastic 121 or Fe-123.
A word of caution There is the distinct possibility that a poorly injected cavity could rust more than one that has not been injected at all. How come? The steel within the cavity that is not coated has a greater potential to rust than the coated steel around it due to all of the electrolytic action being focused on these bare spots. Poor injection equipment and particularly finger operated pumps will not atomise the wax sufficiently and you will get uncoated spots (holidays) within the coating. You will get similar results using a wax that does not flow or is not easily atomised, or by using poor injection equipment. If you have to thin a wax then the final barrier film thickness will be reduced by the amount of thinner you add , 30% white spirit will reduce your dry film thickness by 30%. Heating the wax and using correct equipment will give you good penetration and a good film thickness, perfect for cavity injection.
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If you have found this discussion useful in your fight against rust then I am glad to help. If you have any questions drop me a line and I will answer you personally. Ian Allen
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