Product Specification

Washdown and CIP: Choosing Between 304 and 316L Wire

In equipment that is cleaned in place, the cleaning agent decides the grade more often than the product does. Two stainless parts can see identical product contact and completely different service life, because one is rinsed with chlorinated foam and the other with caustic and water.

This wire is supplied annealed at 550-750 N/mm2 from 0.15 mm to 12 mm in 304 and 316L, bright annealed, bright drawn or pickled. Where chlorinated agents are used anywhere in the cleaning cycle, 316L is the starting point rather than an upgrade.

Three properties of the washdown matter: the active agent, the temperature it is applied at, and whether the part drains and dries or stays wet in a crevice.

Product Specifications

The Agents and What They Do

Sodium hypochlorite

Chlorinated foam and spray are the most common cause of pitting in stainless food equipment. The chloride ion attacks the passive layer, and 304 has little margin against it. Warm hypochlorite is more aggressive than cold, and a part that never dries after the rinse keeps the chloride in contact for hours.

Peracetic acid and hydrogen peroxide

Oxidising agents used at low concentration for sanitising. They are generally compatible with both grades when the concentration and contact time are as specified, but they are normally followed by a rinse, and the rinse quality matters as much as the agent.

Caustic and acid descalers

Caustic cleaning is well tolerated by austenitic grades provided the rinse removes residue. Acid descalers, particularly nitric-phosphoric blends, are used to remove heat tint and scale but need a defined contact time and a thorough rinse, otherwise the surface stays active.

Where the Wire Sits in the Cycle

Traps and crevices

Wire forms create overlaps where two wires touch, and those contact points stay wet after the rinse. Pitting and crevice corrosion start there, not on the open span. Designing the form so it drains is cheaper than upgrading the grade.

Surface and residue

A rough or contaminated surface holds product residue that shields the metal from the cleaning agent and keeps chlorides in contact. Bright annealed or pickled supply, free of embedded iron, gives the cleaning cycle a surface it can actually reach.

Temperature accelerates everything

Every 10 C of cleaning temperature roughly doubles the reaction rate, corrosion included. A cycle that is acceptable at 40 C can be a problem at 70 C on the same grade, which is why cleaning temperature belongs in the grade discussion.

Practical Rules

316L wherever chlorine appears

If hypochlorite is used at any point in the cycle, even weekly, specify 316L. Molybdenum in the 2-3% range is what provides the extra margin, and no surface treatment substitutes for it.

Rinse and drain, do not just spray

The final rinse removes the agent; draining removes the water. A part that keeps a film of water in a crevice has effectively extended the contact time indefinitely.

Avoid chloride-bearing lubricants

Some forming lubricants and marking inks contain chlorides. On a part that will be cleaned in place, they introduce the same ion the cleaning agent does, and they are rarely on the drawing.

Applications

Food processing frames and baskets

Baskets, racks and support frames in 316L, formed from 2-8 mm wire, where foam cleaning is routine and the part cannot be recoated.

Conveying guides and rails

Dry and wet conveying in the same plant, where the wire runs through the washdown zone and the guide material has to match the cleaning regime.

Pharmaceutical and cosmetic equipment

Frames and supports cleaned with defined agents and validated rinse water, where the specification is written down rather than assumed.

Product Advantages

• Grade chosen from the cleaning agent - 316L where chlorinated agents appear, 304 where they do not, stated at order stage.
• Molybdenum stated - the 2-3% Mo in 316L is the reason for the chloride margin, not the grade name.
• Clean surface on supply - bright annealed or pickled, free of embedded iron that would become a pitting site.
• Annealed for forming - 550-750 N/mm2 lets 0.15-12 mm wire be formed into open, draining shapes.
• Limits stated plainly - warm hypochlorite, standing water in crevices and chloride-bearing lubricants are named as the real failure routes.
• Traceable lots - heat number on every coil label with mill test report 3.1 on request.

Quality Control

Rod grade is verified by chemical or PMI check before drawing, including molybdenum on 316L. Diameter is measured inline and at coil ends, tensile and elongation are tested per heat per ISO 6892-1, and surface is inspected for scale, die lines and iron contamination before packing.

Selection and Ordering Notes

1. List every cleaning agent used, including foam, sanitiser and descaler, with concentration and temperature.
2. State whether the part drains freely or holds water in a crevice.
3. Confirm the rinse water quality and whether the part dries between cycles.
4. Give the forming requirement so the shape can be designed to drain.
5. Provide sizes and annual volume for a tolerance and packing review.

Send the grade, diameter, cleaning agents and part geometry for technical confirmation and quotation.