Square Welded Nut

Surface Treatment Introduction

The surface treatment of Square Welded Nut mainly affects its corrosion resistance and adaptability to welding processes. Below are the commonly used surface treatment methods and their characteristics, which can help you select the appropriate one based on the application scenario.

（1）Zinc Plated

Appearance: Blue-white / Yellow / Black

Salt spray test result: 48 - 120

Lower cost

During welding, zinc volatilizes and generates smoke, ventilation is required; thin coating can be welded

Mainly used in indoor dry environments, usually for sheet metal, household appliances, and internal non-exposed parts of automobiles

（2）HDG

Silver-gray thick coating

Salt spray test 500+

Medium cost

The protrusions and surrounding areas must be ground before welding, otherwise fusion cannot be achieved

Applied to outdoor, humid, and salt spray environments (such as building steel structures, agricultural equipment)

（3）Dacromet/Geomet

Color: Matte silver-gray

Salt spray test: 1000+

Cost: Medium

Can be directly welded, with less smoke and no hydrogen embrittlement

Suitable for automotive chassis, it has excellent corrosion resistance and high strength level (it is recommended to choose Square Welded Nut with a grade of 8.8 or above.)

（4）Zn-Ni

Silver-gray/black surface

Salt spray test: 500 - 1000

Higher cost

Can be directly welded, with less smoke

For use in car engine compartments, high humidity environments, as an alternative to cadmium plating

（5）Black Oxide

Color: Black

Salt spray test: 12 - 24 hours

Cost is extremely low

Can be directly welded without any impact

In extremely dry environment, it is only used for temporary rust prevention or as a base layer for painting

（6）Stainless steel in its natural color (No Coating)

Metal original color

High cost

Can be directly welded, but the surface must be cleaned of oil stains

Suitable for strong corrosive environments such as marine, chemical, food, and medical industries

Selecting key factors for surface treatment

When choosing the surface treatment for the Square Welded Nut, you can make the selection based on the following factors.

（1）Welding process compatibility

Direct welding is possible: Dacromet, zinc-nickel alloy, blackening, stainless steel in its natural state, untreated (cleaning required).

Preprocessing required: Electro-galvanizing, Hot-dip galvanizing (the protrusions must be ground).

（2）Corrosion Resistance Requirements

Indoor dry environment: Electro-galvanizing or blackening is sufficient.

Outdoor damp/salt spray: Hot-dip galvanizing or Dacromet coating.

Highly corrosive / marine: Stainless steel 316 or Dacromet.

（3）High-strength grades (8.8/10.9 grades)

High-strength nuts must not be electro-galvanized with ordinary zinc. They should be made of Dacromet, zinc-nickel alloy or stainless steel.

（4）Cost Control

Minimum Cost: Blackening or thin-layer electro-galvanizing.

Overall cost-effectiveness: Galvanized for indoor use; Dacromet for outdoor use (no sanding required, friendly for welding).

If you have specific suggestions for surface treatment in certain application scenarios, please feel free to contact our sales team at any time. We will provide you with free recommendations for the surface treatment of the Square Welded Nut.