Rusty bottom of the car what to do

Cleaning the bottom from corrosion and preventing rust

Many car enthusiasts are familiar with the problem of rust on cars. Drivers are especially concerned about the appearance of corrosion on the galvanized surface of the bottom, since it is known that the zinc layer should prevent these destructive processes from developing. In reality, it is designed to slow down the appearance of rust on the surface of the car and is not able to resist its appearance, especially in salty winter conditions.

Causes of corrosion

The occurrence of rust in the bottom leads to the formation of holes, which causes a decrease in the strength of the entire body structure. This may lead to an emergency situation. Therefore, it is important to know effective methods to help eliminate existing corrosion.

Every time the bottom of a car interacts with bumps on the road or crushed stone that flies out from under the wheels while driving, the integrity of the protective coating is compromised. This leads to the appearance of cracks in the mastic layer. This is where water and dirt will collect - they are obligatory companions of a rusty body. That is why it is important to carry out high-quality anti-corrosion protection of the underbody of the car.

Types of corrosion

There are several types of rust on the surface of a car, depending on which different methods of anti-corrosion treatment are used. According to the conditions of occurrence, the following types of rust can be distinguished:

• gas - appears on the mufflers or exhaust pipe;
• in electrolytes – located in places where moisture stagnates;
• contact rust - appears in areas where metals of different potentials come into contact;
• under friction conditions – observed in places where there is a corrosive environment;
• crevice - in cracks or gaps where water accumulates in contact with oxygen;
• biocorrosion – associated with the influence of microorganisms and their metabolic products;
• mechanical - occurs from impacts of crushed stone flying from under the wheels, tall grass, bumps on the road, which rip off the protective layer from the bottom of the car.

Frequency of anti-corrosion treatment

Checking for rust and the condition of the anti-corrosion coating should be done regardless of whether the car is new or used. Because it happens that even a new car will need to apply additional anti-corrosion protection. If repairs were made or the car was damaged in an accident, the anti-corrosion protection will need to be restored.

Experts believe that inspection should be done once a year. After complete anti-corrosion treatment, the car will be protected for 4-5 years.

Properties of anti-corrosion coating

Any anti-corrosion coating must have the following important qualities:

• abrasion resistance – the ability to protect car parts from regular exposure to abrasives;
• environmental friendliness - rust removal products must be environmentally friendly;
• frost resistance - the product must retain all its properties even at low temperatures;
• high activity - the drug must be well saturated to stop corrosion;
• plasticity - since constant vibrations and deformations are possible during movement;
• the material must be retained on the surface of the car at high temperatures.

Methods for removing rust

Cleaning the underbody of a car from corrosion is carried out in two ways:

• in anti-corrosion centers - where they will quickly and efficiently carry out a complete anti-corrosion treatment of the car;
• Do the bottom treatment yourself, which will help significantly reduce costs, but it will require time and effort.

When choosing an anti-corrosion center, you should talk to the receiver and evaluate his competence and professionalism in order to be confident in the quality of the services provided.

Preparing tools

If you remove rust from the bottom of a car with your own hands, then to carry out the work you need to purchase special materials and prepare tools:

• sanding machine or sandpaper;
• putty knife;
• blowtorch;
• mastic remover;
• metal brush or roller;
• degreaser;
• anti-corrosion primer;
• rust converter;
• putty;
• latex gloves;
• paper mounting tape.

Carrying out rust removal work

Anti-corrosion cleaning of the underbody of the car should be carried out only after washing, since this way you can see all the problem areas. After drying the body, you should begin examining the surface to identify pockets of rust or swollen paint.

The next stage of work is to clean the affected area. Cleaning time directly depends on the method used to remove the old layer of mastic. So, the most time-consuming and tedious method is cleaning with a wire brush or sandpaper. Using a grinding machine, you can prepare the surface for further work much faster.

Important: you need to clean the area 3-4 cm around the rust stain until a smooth and even surface appears.

After the cleaning work is completed, you need to treat the problem area with a degreasing solution and apply a rust converter. Its main task is to transform the rust remaining on the bottom into soil. It is applied using a regular rag. After waiting for the corrosion converter to dry, you can apply a new layer of anti-corrosion coating.

Car protection inside the cabin

Cleaning the underbody of the car from corrosion should take place not only outside, but also inside the cabin. The corrosion process is accelerated by snow that sticks to the soles of boots or the radiator of the heating system.

Therefore, the bottom inside the cabin also needs to be coated with a thin layer of mastic, after having previously dismantled the chairs, carpets and other interior elements.

Most modern cars have a galvanized body. But this is only partial protection against rust, so an additional anti-corrosion coating should be applied.

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Rust is not a death sentence

In the modern world, fighting rust is no longer so difficult, even if you do it on your own, without the involvement of specialists

As long as cars are made of metal, they will rust, despite galvanizing and priming. In the modern world, fighting rust is no longer so difficult, even if you do it on your own, without the involvement of specialists.

A car rusts most when it is standing, especially if it is not in the open air, but in a cold, windproof box. When driving and on the street, the car body is blown and therefore remains more or less dry.

In this material we will talk about different methods of combating corrosion - “old-fashioned” and modern. There are three of them: passive, active and transformative.

The first, passive, is the old “old-fashioned” method, in which problem areas are treated with various kinds of mastics and anticorrosives. The second method appeared with the development of chemical industry technologies: its essence is to periodically treat the body with various kinds of protective agents that are invisible, but at the same time form a fairly wear-resistant film on the surface. The third method is the most interesting and is applicable when the body has already begun to bloom: compounds applied to the rust transform it into soil, which perfectly protects the preserved metal from further corrosion. There is a fourth method, which is often classified as active, but it is better to highlight it separately. This is electrochemical protection, cathodic. Each method should be described in more detail.

Passive way

It can be used on both a new car and a used car. You apply mastic or anti-corrosion agent to the clean bottom of the car, after first removing the plastic or felt protection of the wheel arches. The bottom must be clean and dry. The surface of parts of modern cars perfectly “holds” various types of anticorrosives, and modern mastics are very sticky. However, service and garage pros recommend additional primer. Some problem areas (niches, cavities and seams on the bottom, under the hood and in the doors) should be treated with a polymer anticorrosive agent or a multi-component aerosol based on a mixture of wax and resins. This old “old-fashioned” method has a number of significant disadvantages.

Firstly, it is very labor-intensive and you cannot use it outdoors: you need a garage with a pit. Secondly, every two years it is necessary to carry out preventive maintenance (lubricate, restore, redo in places), otherwise all the efforts of primary treatment will be in vain - in order to protect, the coating must last for many years, but it is washed off, exposing the metal. Therefore, the passive method is used less and less, preferring either the simpler active method, or relying on new developments: the transformative method and electrochemical protection.

Today, few people care about new cars in this way: the owner knows that the factory protection will last for his lifetime, and rust will become a problem for the second or even third owner. More often, additional anti-corrosion treatment is carried out on new domestic cars. For old times' sake. Or they do it carelessly shortly before resale in order to disguise the rot.

The passive method is more relevant on used cars. The process differs from what has already been described only in that before applying primer and mastics, it is necessary to remove existing rust. And here it is better to resort not to the services of sandpaper and white spirit, as in the old days, but to the third method - transformative.

Active method

Active protection is more suitable for a new car. These are various kinds of visible and invisible compounds and varnishes that are periodically applied to the body. It is better to spray a colored composition on the bottom, so that later it will be easier to determine whether it was washed off during use or not. And the paint coating, of course, is a colorless composition or varnish, which, in addition, will make it shine better. Before application, the body, again, needs to be cleaned and dried thoroughly. Under no circumstances apply these compounds to the radiator or engine parts - cooling will deteriorate and the belts will begin to slip. The main disadvantage of this method is not its fragility (for one season), but the fact that it will not protect really problem areas (hidden cavities and niches) from corrosion.

The active method includes treating the body with wax, as well as washing it with special anti-corrosion shampoos.

Transformative method

For many, this method has become a panacea in the fight against corrosion. It's simple, ingenious and doesn't require a lot of time, effort or money. One “but” is the appearance of the car. The fact is that the essence of the method is to treat already rusted areas with a special compound (rust converter). It is based on phosphoric acid, which turns the hated rust into a lead primer, onto which paint can be applied without additional surface treatment. First you need to carefully wipe off any remaining converter that has not reacted. You can do the treatment literally on the go, during stops for at least half an hour: anoint it, wait as long as indicated in the “Method of use” on the converter packaging, wipe off the residue and move on. Without subsequent painting, the car body will not look very aesthetically pleasing, but everything has its time. The main thing at the first stage is to stop corrosion.

Electrochemical protection

This method helps you forget about the appearance of rust on a new car and stop corrosion on an already rusty used car. For this purpose, a special electrical device is used - a cathodic protection station, which is installed in the engine compartment.

The fact is that the rate at which rust appears depends on the electrode potential of the metal. It is enough to shift the potential of the metal into the negative region and the corrosion process stops almost completely. Only the electrodes of the device rust, to which anodic processes are transferred (it is because of them that rust is formed), and only cathodic processes remain on the surfaces of the car, which do not lead to the formation of rust. By the way, galvanizing metal works in the same way - removing anodic processes from the surface. The effectiveness of this method is 99.7%. That is, rust will still appear, but not earlier than in ten years.

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3 real ways to save a car if the body has already begun to rust

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An ominous red spot on the fender, bubbles under the paint at the bottom of the door, suddenly wet floor mats after driving through puddles - all these are signs that the car is already actively rusting. If you start this process, then in just a few years the body will become rotten, for the restoration of which you will have to pay handsomely.

If you look at it, the struggle of car owners with corrosion is a hopeless cause. Despite modern coatings and new alloys, frequent contact with water and aggressive chemicals causes the car body to undergo air oxidation. Rust is especially dangerous for older cars from the 1970s, when car factories used untreated sheet steel. From the appearance of the first stains on the surface to through holes in the body, in fact, only a few years could have passed.

Isolated spots of rust

First of all, corrosion forms in scratches and paint chips. Also, the protective properties of the paintwork are negatively affected by ultraviolet radiation from the sun. And in the event of an accident, the impact sites and bends of body parts need to be “treated” as quickly as possible.

Repairing surface rust is easy. To do this, use an abrasive wheel or sandpaper to remove the paint layer in the damaged area until bare metal is visible. Traces of rust must be completely removed, since even the smallest “dots” will become new centers of corrosion, and the repair will thus go down the drain. The bare metal is primed and then painted.

And to provide additional protection to the car, it would be useful to cover the body with a special synthetic wax.

Large rust spots and bubbles

Body parts made of steel should always be coated with a coat of paint. Even the presence of a chromium or nickel coating does not protect against corrosion. If rust spots do appear, they will grow to the size of spots. It’s even worse if the car drives on snowy roads that are sprinkled with salt. Therefore, it is not surprising that in large Russian cities cars rot very quickly.

When steel turns to iron oxide (rust), it expands significantly, causing blisters underneath the paint. The surface is already uneven and very rough. To remove these irregularities, use a wire brush, an abrasive wheel, and then sandpaper, resulting in shiny metal. Next, as in the previous case, apply a layer of primer and paint.

Through holes

After prolonged aggressive exposure to steel, holes form in body parts. Automakers are actively fighting this, but it all comes down to money. Aluminum or magnesium components are too expensive to replace steel. And anti-corrosion alloying additives (nickel, chromium, molybdenum, titanium) are also limited in use, since they are an order of magnitude more expensive than steel.

As you can see, complete rotting of the car body is a matter of time. But what should the driver do if the power plant is working quite normally, but the rust has eaten right through the bottom and wings? The only way out is to replace parts. As a rule, damaged areas are cut straight out in whole pieces and discarded. To replace them, similar ones taken from so-called “donor” cars (they are found at disassembly sites) or repair spare parts are welded in. The last option, despite the apparent simplicity of the solution, is not always good. And all because these parts are stamped in China and Taiwan, and the cheapest metal is used.

Rust protection

When the car is moving, sandblasting is constantly carried out on its bottom and wheel arches. Therefore, only regular inspection and repair of emerging rye stains will save you from big expenses in the future. For this, various compounds are used (bitumen mastics, Movil), which are applied in a thick layer directly to the bottom. It’s just worth noting that their effectiveness is quite questionable. The author of the website Nobate.ru, while doing body repairs, came across a situation where the bottom rotted, being covered with a layer of “protection”. As a truly effective remedy, we can recommend regular car washing to clean the body and underbody of dirt, salts and dirt, and also check the drainage holes through which rainwater flows. It would be a good idea to fill the internal cavities of the body, including the side members, with oil, which provides significant protection. And the bottom of the car should be treated with gun fat. True, its layer will have to be updated regularly.

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Features of removing rust from the bottom of a car

When inspecting a car from the inspection pit, a rusty bottom of the car is often discovered, but what to do in this case? First you need to understand the cause of corrosion. Knowing this, you can take measures to reduce the harmful effects on the metal of the body.

Why does corrosion occur on the underbody of a car?

The base metal from which most car parts are made is steel; it easily reacts with water or chemicals, that is, it is susceptible to corrosion. Oxidation occurs when iron, the main component of steel, and moisture interact with oxygen in the air. The situation is aggravated by the presence of chemical reagents that are used to eliminate the formation of ice crust on the roadway.

To protect against corrosion, special measures are taken that are aimed at reducing the harmful effects of chemicals on the body material and increasing the mechanical strength of the coating.

The main protective measure is mechanical, carried out in the form of a layer of material that covers the metal of the underbody of the car. Often the bottom and fender liners are covered with plastic elements that absorb impacts from crushed stone and sand.

Types and typical places of corrosion on the bottom

The most vulnerable places:

• wheel arches;
• sections of the bottom behind the wheels;
• hidden cavities in which moisture collects;
• places for jacking.

The process of metal destruction occurs according to the following scenario:

1. In the place where the metal is exposed under the influence of moisture or chemical reagents, the initial formation of rust occurs.
2. Peeling of the protective coating occurs in nearby areas, since iron oxide and hydroxide occupy a larger volume than pure metal.
3. The rust layer has a porous structure, due to which moisture is retained there for a long time. Because of this, the rusting process affects deeper and deeper areas of the metal.

How to react to enamel peeling

Damage to the factory body coating (paint, enamel, anti-corrosive layer) requires immediate intervention. You cannot delay time if you notice an area of ​​exposed metal. In such a place, a corrosion center will form in the shortest possible time, the localization and elimination of which will require a lot of costs, time and materials.

The general idea is that the sooner measures are taken, the easier it will be to stop the destruction of the metal.

Sequence for removing rust from the bottom of a car:

• elimination of peeling areas of paintwork;
• removing rust from the bottom of the car;
• degreasing damaged areas;
• rust converter treatment;
• puttying;
• applying anticorrosive.

How to remove rust

If the bottom of the car is rusty, then this can be fixed at home. Repairing yourself will save you money. There are many ways to remove rust. They all require a two-step approach:

• mechanical restoration;
• chemical exposure.

Using these methods individually only leads to temporary results.

Mechanical method

Whatever cleaning method is proposed, mechanical treatment is always preceded. Sequencing:

• cleaning from dirt;
• removal of areas of peeling coating;
• processing with abrasive material.

The following abrasive materials are used:

• metal brush;
• wire attachment for a drill or grinder;
• emery cloth;
• sandblasting equipment.

The exfoliated areas are removed to those places where the adhesion of the coating and the metal has not weakened. Then the cleaned area is first treated with a wire brush, then with sandpaper. Small and concave areas are cleaned manually, but on large areas it is more convenient to work with a special attachment on a grinder or drill. The abrasive grain size should not be very large so as not to leave deep scratches.

You need to work with power tools carefully, without touching the undamaged coating.

Chemical methods for removing corrosion

The chemicals used to clean the underbody of a car from rust react with iron oxides, dissolving them and converting them into a durable phosphate layer that does not allow moisture to pass through.

Rust removal reagents contain phosphoric acid and special additives that prevent the reagent from interacting with pure metal. Some preparations contain zinc salts, so after drying, not only phosphates are formed on the surface, but also a thin layer of zinc.

Before processing, you need to carefully read the instructions, since the manufacturer indicates whether the drug requires subsequent rinsing or not.

Acid negatively affects the paint coating, so those areas that do not need chemical treatment should be covered with plastic film, strengthening its edges with paper tape. Stationery tape is unsuitable as it is difficult to remove.

The treated surface must be degreased with an organic solvent, since putty, anticorrosive or paint will not stick to greasy stains. Therefore, you cannot touch the prepared surface with your hands.

Which rust repair method is best to choose?

After we have figured out what to do if rust appears on the bottom of the car, we must make a choice. There is no unambiguous definition of the type of processing. You need to act comprehensively, using various methods. Each method has its own advantages and disadvantages.

Advantages of the mechanical method:

• possibility of removing large deposits;
• availability and low price of materials.

• duration and complexity of the process;
• inability to work in hard-to-reach places.

Advantages of chemical treatment:

• • complete removal of corrosion areas;

• preventing further development of defects;
• ease of processing in the most inaccessible places;
• speed of processing.

• low penetrating ability (several microns);
• toxicity of components;
• high price.

How to prevent rust on the bottom

The formation of rust on the underbody of a car can only be prevented by completely preventing metal contact with moisture and oxygen. This is achieved in the following ways:

• electrochemical processing;
• coloring;
• application of a special composition.

The first method is feasible only at the production stage of the car. The last two methods are available for independent use, but conventional painting gives only a short-term effect, since the paint layer does not have the necessary mechanical strength.

Specialized anti-corrosion compounds have a number of positive qualities:

• strength;
• high adhesion (sticking) to the bottom material;
• vibration damping;
• high level of noise absorption.

In addition to protection against corrosion, such products can reduce the level of vibration and acoustic noise in the car interior.

Methods for sealing the underbody of a car without welding

A source of through corrosion, or simply a hole, in the bottom of the car is the price to pay for comfort in the cabin. Its primary source is not anti-icing reagents acting outside, but moisture accumulating under the “pie” of heat, sound and waterproofing. Therefore, when eliminating it, work is carried out mainly from the inside.

If you follow all safety rules when welding, you must completely dismantle the interior, including the trim. This is always very time consuming. Therefore, the question of how to seal the bottom of a car without welding is very relevant. Moreover, most alternative methods do not give worse, but rather better results.

Cold methods of sealing holes in metal

There are two ways to repair holes in the underbody of a car without using hot work.

1. Using composite materials - various types of polymer resins in combination with a reinforcing filler and a curing reaction accelerator. With high-quality surface treatment, in addition to restoring mechanical strength, they play the role of inhibitors - retarders of chemical and electrochemical corrosion reactions;
2. Installing sheet material patches onto rivets.

General technological rules

Holes in the bottom are usually discovered from the outside, when inspecting the car on a pit or lift. Signs of through corrosion are local swellings, which, when you try to pick them out, crumble into dust.

If you find such troubles, you need to open and remove the pie of heat, noise and waterproofing on the floor in the cabin in the entire area where the sheet of iron forming the floor is welded to the power elements of the body - thresholds, tunnel and others. Then you will see the whole picture of the damage and will be able to take preventive measures in those places where corrosion has not yet become through.

Before the process of sealing the holes itself, you need to take measures to slow down the corrosion process (stopping it is an unattainable ideal to strive for). To do this, all iron rags are removed, and the edges that have residual strength are treated with sandpaper and a wire brush until shiny. The cleaned surface is treated with rust converters. For example, the “Tsinkar” composition. Work is being carried out inside and outside.

After completion of the work, the surface of the unprotected metal is covered with bitumen mastics, putty (acrylic, epoxy), paint or gun fat.

The work makes sense if the total surface of through holes does not exceed 15% of the floor area.

Fixing pinholes

If the source of through corrosion has a diameter of no more than 1 centimeter, it can simply be covered with a two-component polymer composition. Poxipol glue or a cold welding kit similar to plasticine gives good results.

A small hole makes it possible to use so-called cathodic electrochemical protection. Find an aluminum rod, make a rivet out of it and fill the hole with it. Within a radius of 20 cm from it, corrosion will stop. True, the rivet will gradually collapse on its own. But this may take five years.

Repairing large-scale damage

In this case, you will have to take care to restore mechanical strength. If the hole is on a flat area, then there is no point in messing around with epoxy and fiberglass.

A truly durable composite material is obtained only with absolutely precise adherence to technology - mixing proportions, drying mode and much more. Use ready-made material of this kind, for example, textolite. Having a thickness of 3 mm, it is not inferior in strength to sheet iron. The plate can only be installed with epoxy glue, but it is better to use a combined connection using rivets. The latter should be made of aluminum, then they will play the role of cathodic protection.

Long holes at the joints with power elements are eliminated with patches made of sheet iron or aluminum. They need to be bent according to the shape of the joint so that the width of the contact zone with the still living material is at least 2 cm. They are installed on aluminum rivets; the use of an epoxy compound would be useful. Especially if sheet metal is used. After all, you cannot know exactly its composition and in which direction electrochemical corrosion will go - whether it will destroy the patch or the body. The polymer resin will act as an inhibitor.

The final sealing of cracks and holes is carried out using, for example, the Novol Plus 710 kit. In addition to the epoxy filler and hardener, it includes a piece of fiberglass.

Is it worth soldering

You can also seal holes in the bottom using soldering. However, ordinary household soldering irons are not suitable for heating metal with a thickness of 0.5 mm or more. Most likely, a hair dryer will not help you with this. You need to use a portable gas burner, for example, Super-Ego R355, which fits into a small - volume from 400 to 700 ml - cylinder for camping stoves.

Solder and flux are required for soldering. The solder used is low-melting, with a predominant content of tin or lead. Flux can be replaced with electrolytic acid. The connection is strong and can withstand high vibration loads.

Soldering has two disadvantages.

1. It involves hot work, which increases the overall complexity of the repair. This can be neglected if your hands grow from the right place;
2. The main material of solder - lead or tin - is a substance that has a lower electronegative potential than iron. Therefore, upon their contact, electrochemical corrosion occurs, in which iron will play the role of a “sacrificial anode” and be destroyed.

Now you have an idea of ​​how to seal the underbody of a car without welding. If you are careful and persistent in cleaning the surfaces, then treating them and protecting them, then the installed patch can outlive the car itself.