How to remove the shipping primer
Transporter Primer (commonly known as Blackey’s Primer) is applied to protect parts against corrosion during transportation and storage.
What kind of substance is it? Sometimes it can be a dry nitro- or alkyd-based paint pigment (carbon black), sometimes nitro enamel, and sometimes something officially unknown to science.
When to remove
Often, especially on the parts of domestic production and various “Made in Taiwan” This miracle can easily be applied on a greasy surface and have rough spots.
At higher quality non-original parts shipping primer can look better and even have a nice gloss. But it does not make much difference. In most cases, this coating is not suitable as the first layer of the system. It does not have sufficient adhesion to the metal and does not properly protect it from corrosion. Therefore, it must be removed, permanently and irrevocably.
How and what to remove
So, the first thing to do is to make a solvent test or, simply put, to put a rag soaked in solvent for 5 minutes, because sometimes “black” is easily washed off. But if the detail has been lying somewhere for a long time, this coating becomes hard enough and may not come off.
In this case we’ll resort to grinding (for example with abrasives P100-P120 or a disk type Roloc ( 3M ) or Siastrip ( Sia ). But if on the face side of the detail the “niello” can be carefully sanded off, from the perforated and the more so from the inside it is almost impossible to remove it completely. And there is no need to. After all, we are going to cover the part with primary anticorrosive primer, and it has an excellent penetrating ability and can provide sufficient adhesion. But where possible, of course, the shipping primer should be removed as much as possible.
After removing the primer, if the part does not need a filler, you can safely paint it with the “wet-on-wet” method.
When not to remove
On body parts from reputable manufacturers, the black primer may be a cataphoresis coating applied by immersion. By and large, not removing black primer is the only time to do so. But even so, it will be not superfluous to throw a rag with solvent on it (well, I can’t trust the black primer, at least be warned).
If you have absolutely brand-name gray or gray-green color in front of you, you must be dealing with cataphoresis.
Rejoice. All you have to do in this case is mat the part with P320, apply primer-coat and paint. Areas of bare metal, if any, should be precoated with an anti-corrosion primer.
This is interesting.
Besides solvent test there is one more simple way to check the quality of adhesion of one material to another (in our case the shipping primer to the metal).
It gives an approximate, but quite sufficient visual assessment of the quality of adhesion. Everything is simple. We take sandpaper P240 and dry sand the area to be checked up to the metal. If the transition boundary is uniform, does not peel off in spots and not crumbling – adhesion is sufficient.
If you want to “scientifically”, there is a special device for testing adhesion, which is a ten sharp blades parallel to each other at a distance of one millimeter. They are made several cross-notches on the tested material, and then, by the number of squares dropped out, the conclusion about the quality of penetration of one material into another. This method is called the lattice notch method.
If the painter doesn’t care what the primer is on the part, the results of painting will be as predictable as a game of Russian roulette.
Gray and black
If the car is thoroughly “beaten by life”, the replacement of body parts becomes essential: fenders, doors, sills, panels. So we go for new parts – as a rule, on the market.
Most new body parts come on the market with a primer coat already applied.
We are not going to talk about branded “gray” parts, nicknamed so for the color of the primer, applied to the phosphated metal. God let the plants process the body itself according to such technology – there’s no time for spare parts.
If you are lucky enough to deal with such a part, all you need to do is to lightly, as they say, mat the surface (P320 or Scotch-Bright), blast it, degrease, apply primer filler and then – topcoat enamel.
But that’s not what we’re talking about now. We are interested in other, “black” parts, of which there are most.
Black coating is applied to protect metal from corrosion during storage in warehouses, during transportation. Probably that’s why this primer is commonly called “shipping primer”.
Should I remove it or not?
Many experts advise to remove it completely from the surface of the metal and only after that perform further work on the part. This operation can be performed in different ways: by grinding, sandblasting, using a flush. At one time, such actions were quite justified.
This coating got its bad reputation in the last millennium, when stamped body elements of domestic production could be covered with anything, up to a simple nitro paint, which could easily be applied to the oily surface and have rough edges. The removal of such a “primer” due to its low resistance was not very difficult: in most cases it was just a matter of “soaking” the part in solvent.
But what about the removal of the shipping primer on modern body parts? Is there any point in carrying out such an operation nowadays? Especially since it is planned to do it not only from the front part of the part, but also from the inner surfaces of the door or hood, for example. And this is not easy.
On modern repair parts from reputable manufacturers, the black coating is usually a cataphoresis anticorrosive primer, applied by immersion. The cataphoresis coating is applied by electro-deposition in galvanic baths, where the primer particles diffuse (penetrate) into the surface of the part, which gives the coating high strength and anti-corrosion characteristics.
Therefore, with the exception of the surface damaged during transportation, there is absolutely no need to remove such coating. It is enough just to mat it (P240-P320), and if the part does not need puttying, you can safely prime and paint it by “wet-on-wet” method, or by standard technology.
At the same time, prolonged storage of new parts in warehouses can lead to failure of the adhesive properties of the shipping primer and the emergence of corrosion foci under it. In this case, removal of the primer is considered mandatory. This can be done, for example, with consecutive use of abrasives with grit sizes P120 and P220. You can also use a Roloc (3M) or Siastrip (Sia) type disk.
New car body parts, in most cases, have a black coating. This is the factory primer. If the body plate is original ( OEM ) or from a certified manufacturer, it is coated with the so-called cataphoresis primer, applied by electro-deposition.
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At the factory, the part goes through several processing steps. First it is degreased, phosphatized and then coated with a primer using electrodeposition in a special tank. As a result, a phosphate and polymer protective film is formed. After application, the factory primer is “baked” at 150 to 200 degrees Celsius. This causes it to fully polymerize and become more durable and chemically inert. Cataphoresis primer is mostly epoxy in composition and is a good protective anti-corrosion coating.
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Cheaper body parts may have a shipping primer, which is not a durable protective coating and must be removed.
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Cataphoresis primer on the surface of the body panel has a very thin layer. It has the following advantages:
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- It has a strong bond to the metal surface.
- The primer layer obtained in the factory by electrodeposition is very even and uniform (has the same thickness everywhere) over the entire surface.
- The primer covers the entire part, including hidden cavities.
- The coating does not contain any unnecessary impurities.
- It has anti-corrosion and adhesion properties.
How do you know what kind of primer the part is covered with?
Visually the cataforesis primer has a matte finish with slight gloss. If the coating is matt, has no gloss or has a fairly high gloss, it is probably not a cataforesis primer.
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To determine the type of primer, soak a rag in solvent (646, 647 or acetone) and place it on the surface of the new body part. After waiting 10 minutes, remove the rag and look at the result of the solvent. If the coating did not change in any way and left no traces on the rag, then it is very likely to be a quality cataforesis primer. If, however, there was peeling of the coating, then such a primer is not a cataforesis primer and will not serve as a good base for the paint coating.
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How to prepare the part for painting with the factory primer?
It is better to remove the doubtful primer to clean metal by sanding. Then you can spray primary and secondary primers and paint.
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A good quality cataphoresis primer, provided it is intact and free of defects, can be left on the part.
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Paint manufacturers recommend applying a secondary primer on top of the cataphoresis primer to increase adhesion and reduce chipping in service. Acrylic two-component primer can be used. The factory primer is ground with abrasives P240 – P320, degreased and primed. An additional advantage of priming over the factory primer is the use of a primer of a color similar to the color of the paint that will be used to cover the part. As a result, less paint will be used. That said, you have to understand that sometimes manufacturers recommend things that make the repair more expensive and can be done without.
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Many of the craftsmen I have talked to have painted over the factory primer many times in a row, pre-preparing it for painting, and there have been no problems because of it.
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They believe that if the surface is a true cataforesis primer, you can scotch-brite or other paint abrasive, degrease, and paint over it. A real cataforesis primer stays on the surface very well and is hard to sand. It has a stronger bond to the surface than epoxy primer applied with a paint gun.
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Some service centers, in order to comply with regulations and give a long warranty on their work, grind the factory primer to bare metal and then apply primary and secondary primer, then prepare the surface and paint.
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In summary, we can say that if the factory primer is good quality, the part has no traces of rust, it makes no sense to remove it. Thus, you will save time, save the phosphate factory film and leave additional anti-corrosion protection in the form of cataphoresis primer. As written above, it is not superfluous to apply a secondary acrylic primer on top, tinted to match the paint, which will be painted part. This way you will at least get the benefit of saving paint consumption.
The shipping primer: Should I remove it or not?
Preparing
If the painter doesn’t care what the primer is on the part, the results of painting will be as predictable as a game of Russian roulette.
Gray and black
If the car is thoroughly “beaten by life”, the replacement of body parts becomes essential: fenders, doors, sills, panels. So we go for new parts – as a rule, on the market.
Most new body parts come on the market with a primer coat already applied.
We’re not going to talk about proprietary “gray” parts, nicknamed so for the color of the primer applied to the phosphated metal. May God help plants to process bodyworks according to this technology – there’s no time for spare parts.
Cataphoresis primer
If you are lucky enough to deal with such detail, all you need to do is to lightly smear the surface (P320 or Scotch-Bright), blast, degrease, apply primer filler and then – topcoat enamel.
But that’s not what we’re talking about now. We are interested in other, “black” parts, of which there are most.
Black coating is applied to protect metal from corrosion during storage in warehouses, during transportation. Probably that’s why this primer is commonly called “shipping primer”.
Should I remove it or not?
Many experts recommend completely removing the black shipping primer from the surface of the part and only after that do further work with it. This primer can be removed in different ways: by sanding, sandblasting, using a flush.
At one time, such actions were quite justified. In fact, previously on the stamped body parts of domestic production as a shipping coating could be applied anything, up to a simple nitro paint. It could easily be applied on an oily surface and have some rude stains. Because of its low resistance, the removal of such a “primer” did not pose any problems – in most cases it was just a matter of “soaking” the part in solvent.
But what about the removal of the shipping primer on modern body parts? Is there any point in performing this operation now? Especially, if you want to remove the primer not only from the front part of the element, but also from the inner surfaces of doors or hood, for example. And this is not so easy!
On the modern parts by reputable manufacturers the black coating is, as a rule, the anti-corrosion primer, applied by cataphoresis immersion method. The cataphoresis coating is applied by means of electro-deposition in galvanic baths, where the primer particles diffuse (penetrate) into the surface of the part, which gives the coating high strength and anti-corrosion properties.
Therefore, it is not necessary to remove such coating, except for the surface damaged during transportation. You just need to prime it (P240-P320) and if the part doesn’t need any filler, you can safely prime and paint it by “wet-on-wet” method or according to standard technology.
However, storing new parts in warehouses for a long period of time can cause the primer to fail to adhere and result in corrosion spots under the primer. In this case, removal of the primer is mandatory. This can be done, for example, with consecutive use of abrasives with grit sizes P120 and P220. You can also use a disc type Roloc (3M) or Siastrip (Sia).
Removing the Transfer Primer
