Welding Stainless Steel: Best Practices for 304 vs. 316 Grade Fabrication

Unlike mild or carbon steel, stainless steel contains chromium and other alloying elements that form a protective oxide layer on its surface. This layer gives stainless its corrosion resistance but it can also complicate welding.

When stainless is heated, chromium can combine with carbon to form chromium carbide at grain boundaries. This process, known as sensitization, reduces corrosion resistance near the weld zone if not controlled properly.

To prevent this, experienced welders use techniques that minimize heat input, maintain shielding gas coverage, and control cooling rates. Each stainless grade responds differently, which makes grade-specific knowledge crucial for consistent results.

Both 304 and 316 stainless steel belong to the austenitic family of alloys, prized for corrosion resistance, ductility, and weldability. The main distinction lies in their chemical makeup specifically, the addition of molybdenum in 316.

The molybdenum in 316 enhances resistance to pitting and crevice corrosion, making it ideal for harsh or saltwater environments. However, it also slightly changes how the alloy behaves during welding, influencing filler selection and heat control.

Grade 304 is the most widely used stainless steel and fortunately, also one of the easiest to weld. Its stable austenitic structure allows for smooth, consistent welding with minimal risk of cracking or warping, provided proper technique is followed.

Common welding processes for 304 stainless include:

• GTAW (TIG): Preferred for thin sections and sanitary-grade welds due to superior control and clean bead appearance.
• GMAW (MIG): Efficient for thicker sections or higher production runs, offering good penetration and speed.
• SMAW (Stick): Used in field repairs or non-sanitized fabrications when shielding gas setups aren’t practical.

For 304, it’s critical to:

• Use low-carbon filler metals (like ER308L or E308L) to reduce carbide precipitation.
• Maintain proper shielding gas flow (typically argon or argon-helium mixtures).
• Avoid overheating excess heat can discolor the surface and reduce corrosion resistance.

After welding, chemical passivation or mechanical polishing restores the oxide layer that protects against corrosion, a standard step at Action Stainless for food-grade and architectural applications.

Grade 316 offers improved corrosion resistance thanks to molybdenum, but that element also affects how the alloy reacts to heat. During welding, molybdenum can segregate at grain boundaries if cooling is too rapid, which may slightly weaken localized corrosion resistance.

To prevent these issues, welders should:

• Use ER316L or E316L filler metals that match base metal composition.
• Control heat input carefully to prevent sensitization.
• Maintain steady gas shielding throughout the weld to avoid oxidation.

316 is particularly popular in industries such as marine fabrication, pharmaceuticals, and chemical processing, where weld quality directly impacts equipment longevity. For these environments, Action Stainless often combines TIG welding with controlled heat zones and post-weld passivation to ensure complete restoration of corrosion resistance.

After welding, stainless steel must be cleaned and restored to regain full corrosion resistance. Even with perfect weld penetration, discoloration or oxidation can form on the surface, compromising the metal’s protective layer.

Common post-weld treatments include:

• Pickling: Chemical removal of oxides and scale.
• Passivation: Application of nitric or citric acid to reform the chromium oxide layer.
• Mechanical polishing: Smooths welds and removes surface imperfections for sanitary or aesthetic applications.

For critical industries like food, beverage, and pharmaceuticals, Action Stainless performs these finishing steps on-site to ensure hygienic surfaces and uniform appearance across assemblies.

Shielding gas is one of the most critical factors in stainless steel welding. Argon provides excellent coverage for TIG and MIG processes, while helium blends increase penetration for thicker sections. For both 304 and 316, gas purity must remain high to prevent porosity and contamination.

Filler selection is equally important. The filler must match the alloy’s chemical composition while maintaining low carbon content to resist carbide formation.

• 304 typically uses ER308L or E308L filler.
• 316 requires ER316L or E316L for best results.

Using incorrect filler can lead to mismatched corrosion resistance between weld and base metal, reducing long-term performance.

The strength and appearance of a stainless weld often determine a product’s suitability for its environment. For example:

• Food processing equipment demands smooth, crevice-free welds that resist bacterial buildup.
• Marine components require complete protection from salt exposure and pitting.
• Pharmaceutical systems need polished, contamination-free welds that meet strict regulatory standards.

Action Stainless’s welding teams follow specific procedures for each of these sectors, balancing throughput with the highest possible finish quality.

Even small errors can lead to major performance issues in stainless fabrication. Key issues to avoid include:

• Inadequate shielding gas coverage, which causes porosity or oxidation.
• Excessive heat input, leading to distortion or grain boundary sensitization.
• Improper filler matching, resulting in uneven corrosion resistance.
• Skipping post-weld cleaning, which leaves discoloration and weakens the passive layer.

Following consistent weld procedures like those used at Action Stainless prevents these issues and extends component lifespan.

Stainless welding is both a science and an art. With in-house expertise, Action Stainless handles projects that require tight control of heat, finish, and geometry from precision TIG welds to high-strength structural joints.

Because welding is performed alongside cutting, machining, and grinding, each stage is carefully coordinated to maintain dimensional and aesthetic quality. This integration reduces rework, improves part alignment, and ensures every weld meets customer and industry standards.

Both 304 and 316 stainless steel offer outstanding weldability, but each requires specific attention to filler selection, heat control, and finishing.

• 304 remains the versatile choice for general fabrication and food-grade applications.
• 316 delivers superior corrosion resistance for marine and chemical environments.

By applying controlled welding techniques, proper post-weld finishing, and integrated fabrication processes, Action Stainless ensures every stainless weld performs as intended clean, strong, and corrosion-resistant for years of service.

For manufacturers seeking reliability in welded stainless components, partnering with a facility that understands both the material and the process makes all the difference.

Contact Action Stainless to discuss your 304 and 316 stainless fabrication needs and receive guidance on the best welding process for your application.