Welding the underbody of a car: tips and equipment review

The underbody of the car is exposed to water, dirt and road chemicals more quickly than the rest of the body. And if you drive over a high curb or asphalt ridge, the deformations accelerate the deterioration of the metal even more. By the way, from personal sad experience, I note that it is better to drive over such obstacles with your wheel, and not take them between the wheels, if the ground clearance is less than 160 mm. So, I’ll tell you how to repair the underbody of a car by welding, which devices I consider the best for this, and I’ll share the specific nuances of the welding process.

Semi-automatic welding of car underbody

I consider this method to be the best because the work is easier and completed faster. For welding the bottom of a car with a semi-automatic machine, I recommend the following models:.

• PTK MASTER MIG 180 F15 is a simple and reliable budget semi-automatic machine for the garage. If you want to cook the car yourself, this is a great choice.
• Svarog REAL MIG 200 (N24002N) is also a simple device, but at 200 A (can be useful for welding thicker metal, such as gates, wicket hinges).
• AuroraPRO OVERMAN 200 is another budget device for repairing the bottom by welding, but it is capable of working when the incoming voltage drops up to 140 V. This is relevant if your garage has such problems with electricity.
• Fubag INMIG 200 SYN Plus is a semi-professional machine, which should be considered by car service technicians and craftsmen. Fine settings will ensure comfort when working with bottom metal.
• KEMPPI MinarcMIG EVO 170 is a reliable and durable semi-automatic machine with a graphic display. With a current of 100 A, you can cook continuously, which is important for long-term work in a car service station.
I recommend that the welding wire for repairing the underbody of a car be copper-plated. Then the seam will better resist the constant vibrations present on the body. Buy, for example, ESAB OK Autrod 12.51 wire with a diameter of 0.8 mm.

Types of service

Overcooking the bottom of a VAZ-2112 car can be:

1. Using semi-automatic welding equipment:
2. Using gas welding.

Depending on the location of the repair, the service is:

• In the garage of a private master.
• On the territory of the car service center.
• At the location of the client's car.

Depending on the time that the client allocates for work, overcooking occurs:

According to the performer, overcooking is classified into:

Manual arc welding of car underbody

Welding the underbody of a car with an electrode and an inverter is slower than with a semi-automatic machine, and the welder himself must already have certain skills to control the arc (it’s easier for beginners to work with a semi-automatic machine). I don’t recommend this method for professional work due to the low speed, but for welding the underbody of a car with your own hands it is quite suitable. The price of RDS inverters is much more affordable than semi-automatic ones. If you are thinking about buying a welding machine, I advise you to take a look at:

I advise you to buy ESAB OK 46.00 electrodes with a diameter of 2-3 mm. They are suitable for welding in all spatial positions and are unpretentious to the cleanliness of the metal surface. Other welding machines suitable for welding the bottom can be found in the adjacent article about choosing equipment for a garage. If you are seriously thinking about opening a service station, also consider models suitable for welding alloy wheels.

Price list

Details Author: Super User Category: Sample Data-Articles Published March 17, 2016

Wheel alignment prices*

TO prices*

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Preparation of the bottom before welding

Now let’s talk directly about the process of repairing the bottom by welding. First, the surface needs to be prepared. Ideally, it is better to sandblast the bottom to see the full picture of the condition of the metal and make it easier to initiate an arc. If you don't have a sandblaster, brush the metal to remove any rust.

Tap the surface with a hammer, looking for ringing, resonant places - the iron is thinnest there.

Open holes should be cut out with a grinder to solid metal, otherwise the material will continue to rot even inside the structure. Use tin snips in hard-to-reach places. Prepare cut segments that match the shape of the areas to be closed (patches). Metal thickness is acceptable 1-2 mm.

Body work

Price list for body and paint work at the Autoliga shopping center

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The nuances of welding the underbody of a car

I won’t describe banal things about disconnecting the battery terminal, etc. - I’ll tell you about the non-obvious. First, the age-old question, which should generate many comments under the topic: should the bottom be welded end-to-end or overlapping? There are pros and cons to each method. The patch strictly along the contour of the hole in the bottom looks neat, but you will have to apply a continuous seam. There is a high risk of metal deformation and subsidence. It will overheat, which will worsen its strength characteristics and corrosion resistance. With the butt method, it will take a long time to adjust the size of the patches to avoid wide gaps.

Overlapping patches look less attractive, but it's under the car, so who sees them there?! But overlap welding:

• possible pointwise, which means faster;
• occurs without deformation;
• two layers of metal form an additional stiffener;
• the material overheats less and resists corrosion better later;
• Due to the tacks, the patch better tolerates the “play” of the body metal in motion.

My opinion is to over-cook. Apply the metal and tack. Then it is welded in short seams of 15-20 mm at the same intervals. Light the arc on new metal and transfer it to the joint - this will result in fewer burns. To avoid an “accordion”, weld the joint not from left to right, but start from the end of the joint, but make each seam from left to right. See our article for even more details on welding body metal.

How to treat the outside of the bottom after welding

If the bottom is not covered with a protective layer, it will rot over the next couple of years. Confirmation is the service life of the muffler can - it is not treated and lasts for a maximum of 3 years. And we also have an intermittent seam, where moisture will get in. I suggest this procedure and how to treat the bottom of the car after welding from the outside:

1. Cover the metal with body primer.
2. Let it dry.
3. Treat with bituminous compounds “Bitumen Anticorrosive”, “Epoxy Autoanticorrosive”, “Bitumen Mastic”.

These are elastic products that adhere well to a vibrating surface. Pay special attention to the joints to fill the gaps. Inside the cabin, I recommend, if you have access to the joint, to apply sealant or blow it with wax.

Price list (cost of work)

Price list (welding works)*

Price list (painting work)

Price list (threshold production)

* Attention! the final cost of welding work is determined only after opening the damaged areas of the car.

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