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Cavity Restoration

Cavity Restoration


Step 1: Rust Removal

If the bodyshell is sound, rust removal and treatment of the damaging chemicals by FERTAN Rust Converter is necessary as a preparation for the final protection which will follow.

To achieve this the product should be injected into all the box sections by a cavity injection gun and a 360° probe. Take care to ensure that with a pressure gun the pressure is kept at 108 – 138 PSI and with a cavity gun it is at 43-58 PSI. Use of a hand spray gun is only recommended for doors, bonnets, etc., because this can only be used with a very low pressure and that is not sufficient for complete atomization of the FERTAN Rust Converter product in normal box sections. Please note that the product must penetrate in all cavities, seams, and double-skinned areas to work effectively. On vehicles with loose flakes of rust which peel off and lie on the base of the box sections, two applications of FERTAN Rust Converter are recommended, because these flakes must firstly be sufficiently loosened that they can later be removed by rinsing with water. FERTAN should not be applied at temperatures of less than 45° F.


After the reaction time has elapsed rinse the box sections and cavities thoroughly with water. Use approximately 15 qt. of water for every quart of FERTAN Rust Converter used and operate the pressure gun at a pressure of 87 PSI and the cavity gun at 58 PSI. For this important rinsing do not park the vehicle on a pale surface, tiles, paving stones, etc., because the run-off water will stain them.

To be able to treat box sections and cavities to the best effect with a cavity gun, all the water drain holes present in the body must obviously be opened up. If they are blocked, covered with underbody protection or are not present, new holes should be made in areas which do not affect the appearance or integrity of the bodywork. When doing this, please firstly obtain suitable sealing grommets and then drill holes of the correct diameter, and while drilling the holes coat the drill bit with grease so that no swarf can enter the box section, as this could cause corrosion later.

Drill the holes in such a way that all the cavities are accounted for and make notes on a piece of paper to ensure this is the case. If a box section plan is available from the manufacturer, this should obviously be used as a guide. To ensure that no rinsing water remains in the seams and low points, raise the vehicle with a jack (e.g.) firstly the left front, then the left rear, and so on, and allow the water to run out completely. When the box section or cavity has been rinsed out completely, it is free of rust and damaging chemicals and after the surface has been dried it can be coated with wax.

What happens chemically?

Here we would like to explain the operation of FERTAN Rust Converter, particularly in box sections and cavities. The product has three main constituents, and they facilitate the removal of any Fe3, rust present, as well as mineral salts and acids, via their combined effect. In this way the bare metal is exposed and simultaneously provided with a zinc phosphate coating as a cathodic protective layer. This is then additionally protected by an Fe3-free tannin complex (known as HOPEITE

Zn3(P04).2 4H20 and Phosphophyllite Zn2Fe(P04) 4H20. This layer is absolutely insoluble in water and protects the metal for at least six months, during which time the protective treatment of the box section or cavity should be carried out. In order to remove the loosened rust particles as well as the pollutants and damaging substances, the cavity or box section should always be very thoroughly rinsed with water. In this instance it is advisable again to observe the rule of thumb: 15 quarts of rinsing water for every quart of FERTAN Rust Converter. The rinsing water used in this process can’t cause any new corrosion, because the layer which has been created on the surfaces of the box section is completely insoluble in water, and it should also be kept in mind that the running water thins the electrolytes and lets them run off in the rinsing water, which noticeably hinders the rate of corrosion. Please dispose of rinsing water in an environmentally responsible way after use.


Step 2: Pre- treatment

Option 1: FERTAN Cavity Protection Wax Application

Protective wax should whenever possible be built up in several thin layers. In the process allow at least 12 hours drying time between coats. In this way the solvents can evaporate and the tiny cracks which unavoidably open up in each coat can be closed up by the following coat. In this way a very stable, durable, and long-lasting final protection is built up, which

is considerably more stable than a thickly applied coat which can begin to show cracks again after a number of years. In this way it is similar to paint, where several thinly applied layers are notably more stable and durable than a thick coat applied in one layer. The recommended pressure for applying cavity wax protection is 108 – 138 PSI for a pressure gun and 43- 48 PSI for a cavity gun.


Option 2: FERTAN Corrosion Preventative Grease Application

Spray comes with 360° nozzle and probe for easy application. The metal surface should be free from dust, loose parts and rust. If rust or corrosion is present remove this with FERTAN rust converter. Suggested temperature (material and car body) 50 – 85° F. Dry film thickness about 50 ppm. Higher film thickness, applied as a second coat, increases durability.




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