Weld Through Primer: Complete Guide And Best Products

Any structure that is made out of steel has to be protected from the elements. One area that is sometimes overlooked is the welding seams. As a marine engineer, I have learned some ways to protect thousands of miles of welding seams in ships. So, I decided to write a guide about weld through primers because I have noticed that welders have a lot of questions about them. In this article, I will mention some basic facts about primers and how to use them. Let’s get to it.

What Is A Weld Through Primer and Do I Really Need It?

So you’re ready to start your welding project. You have your equipment, your welding material, and your plan of how the project should go. There may be one thing you are missing and that is weld through primer. It goes directly on the metal surfaces you are planning on welding. Weld through primers are zinc-based products (some may be copper-based, but that is rarer) that are applied directly on your metal material surfaces before you begin your welding project.

You may wonder how to prevent your weld from getting rust or how to protect your weld project from corrosion. A simple and powerful way to do so is buying and utilizing, weld through primers. You may also wonder about the type of welding project you wish to undertake. It may be difficult for you to apply the primer directly onto the material, especially if you have a lot of overlapping pieces being welded. Luckily, it may be easily applied via a spray nozzle or a brush, and you can apply the primer before and after the weld to fight any possibility of corrosion or rust occurring. The key to a successful and long-lasting weld is by purchasing and using weld through primer.

Basic Tips About Primers

Primer makes the process easy; you must be sure to clean welding materials before you begin to ensure a clean start to the welding process. Weld-thru primer was created to prevent any rusting or corrosion of the materials being connected and to keep your weld rust-free after the process is completed. In fact, the very purpose of weld through primer is to prevent rusting of any kind. Weld through primer protects the newly connected joints from rust, as well as the inner edges of the welded material.

A precaution you need to take before you begin the welding process is that all welding material needs to be clear of any substance that might contaminate the process. Weld failure might happen if you do not take such precautions before performing the weld. The predominant type of contamination in steels is rust. When you plan your welding job or project, you need to make sure the material you will be using is free of moisture, dirt, rust, and corrosion. Also, once the weld is completed, you must ensure to keep the welded joint area protected from rust.

How Do Weld Through Primers Work

As stated previously, weld through primers are designed and manufactured for the purpose of keeping your welding materials rust-free and corrosion-free. They are applied by hand, brush, or spray nozzle to the metal material about to be welded upon. The weld through primer prevents rust and corrosion from occurring because while the welding process occurs, the applied weld through primer turns into a liquid and runs into the weld pool to fortify the welded materials from encountering any rust or corrosion problems down the road.

Where Did Weld Through Primer Come From?

Weld through primer came about because of the steel construction and the shipbuilding industries. These manufacturing industries were known to use up a lot of sheet metals, plates, and rods. The metals would be produced at the steel mills and then transported long distances. The distributed metal materials would be stored onsite at the destination (shipyards or steel construction sites), and would be put in storage for a long span of time until they were used as welding material.

A common problem arose from this method of storing and using the metals after a long length of time: rust and corrosion kept happening to the metal materials. This would mean that the industries could not use the rusted materials and they were declared worthless. Since this pattern kept occurring, and manufacturers were losing money, a solution had to be made to keep the metals from becoming rusted. Weld through primer was then invented and applied to the metal before being shipped off to the job sites. This kept the metals for welding preserved from rust and corrosion, and they could be kept in storage safely until it was time for them to be utilized.

What is the Best Weld Through Primer Available on the Market?

There are quite a few options and varieties of weld-thru primer available for you to purchase. A popular place to buy the weld through primer is off of Amazon, but you can also buy the primer at your local hardware store. Below are the best options of weld-thru primer for you to purchase for your next welding project:

  1. Dupli-Color DPP108 Prime: This primer a very durable primer and is quick at drying. The time the primer takes to dry is quoted at 15-30 minutes. This primer cleans and seals the metal to guarantee that you have better corrosion resistance. Dupli-Color Primer has a zinc coating that is able to be applied to dry metal surfaces. Not familiar with applying weld through primer? Do not worry! Weld through primer is very easy to apply. Another benefit to this primer is that it is a gray color that works with most metals. You can find this here on Amazon.
  2. 3M 05917 Weld-Thru Coating II: This is a 3M product, which means you will get very effective corrosion prevention. This is also a zinc powder-based weld-thru primer. The 3M Weld Coating boasts a durable coating that is put on the dry metal materials easily due to an aerosol spray design. The gray color of the zinc powder base blends in with most materials. The drying time on this spray is around 10 to 20 minutes. This product is available on Amazon and it comes with a one-year warranty on the weld protection guarantee.
  3. U-Pol Products 0768 Zinc/Copper Weld: This weld through primer offers two formulations. You can choose between zinc or copper-based primer. This specific brand of primer works best with rust prevention, so keep that in mind if you are in an area with a lot of moisture or humidity. Also, this primer may be applied to a variety of welding material surfaces. That includes metals, aluminum, or galvanized material surfaces. Both the copper and the zinc formulations dry around 10 to 20 minutes after the application of the primer. You can check it out here on Amazon.

When Should Weld Through Primer Be Used?

Weld through primer should be used in a number of welding project situations. Weld through primer can be applied at the very beginning; before you even start the welding process. This will keep your metals protected while they are being stored.

Another situation you would need to apply weld through primer is if your materials are different colors, such as red or black. These colors, while unique, are known to have more rust or corrosion problems down the road if they are not properly protected with primer. If you envision painting your weld project after the weld is complete, you will definitely want to apply weld through primer onto the metal material. Paint may help seal the metals from rust or corrosion, but you cannot apply paint as easily as a primer does it. Some spots may be missed when you paint the joints or edges of the weld.

One last possible situation that weld through primer would be useful, would be if you have a lot of overlapping or overhanging metal parts. The under-hanging pieces would need to be addressed with primer because dirt or debris could easily infiltrate that vulnerable area.

A good rule of thumb is to apply at least two coats of weld through primer on the metal you are about to weld. Remember to factor in drying time between the coats, and do not start the welding project until at least thirty minutes after you apply your final primer coat. Do not rush this process, because a little time waiting will save you future headaches.

There are a few situations were weld through primer would not be beneficial, and that includes if you have aluminum as a material. Also, some brands may leave your weld brittle. If you buy from the suggested brands above, you should not run into that problem. However, be sure to check reviews before purchasing your primer just to make sure it is a solid product.

In conclusion, when should weld through primer be used? If you are welding metal, you would be wise to use it in most situations. This not just a precaution, but also a helpful hint to ensure that a weld joint or project remains clear from rust.

Final Thoughts

Welding is used every day and within a variety of industries. You do not have to be a professional welder to perform welding projects at home, but please be advised to take a basic welding course or read a few more articles on the subject before you attempt to try welding on your own. When you do get the chance to weld, be sure to invest in some weld through primer. This will keep your weld project strong and durable for the long haul!

4 thoughts on “Weld Through Primer: Complete Guide And Best Products”

  1. Very helpful… I am installing a pair of steel sub-frame connectors on a vehicle which requires welding. The weld through primer looks like the correct procedure for the install appreciate the knowledge.

  2. I bought some Galv primer from Screwfix which says that it is suitable to weld through.
    Is it as good as the others that you recommend.

    • Thank you for the comment, Patrick. It’s always welcome to receive feedback from my readers. I will check your suggested product once the appropriate occasion arises.


Leave a Comment