1.2316 Corrosion Resistant Mold Steel Corrosion Protection: How Does 16% Cr Protect Your Mold?

Type 1 Corrosion: Pitting Corrosion

Pitting corrosion is the most common and dangerous corrosion type for 1.2316 Corrosion Resistant Mold Steel. It happens when chloride ions attack weak spots on the anti-rust film. A tiny rust dot like a pinhead forms first, then eats deep into the steel. Only a small spot shows on the surface, but a big pit forms inside. It looks just like an iceberg; the hidden part under the surface is much larger.

HCl gas released during PVC injection is the main cause of pitting. 1.2316 corrosion resistant steel handles chloride ions far better than P20. Molds made of P20 for PVC may get rust marks after only 20,000 to 30,000 shots, while 1.2316 can last over 200,000 shots. Still, it cannot stop corrosion forever. The risk of pitting rises sharply in strong acid conditions with pH below 4, or hot and wet environments with chloride ions.

Corrosion Type 2 of 1.2316 Corrosion Resistant Mold Steel: Crevice Corrosion

Crevice corrosion takes place in narrow gaps of molds, such as sliding fitting surfaces, insert joints, areas around ejector pin holes and dead zones of cooling water channels. The working rule is low oxygen inside gaps and thick gathered liquid, which forms tiny local batteries to speed up corrosion. When you spot rust on the mold surface, deep slots may have already been corroded deep inside the gaps.

Corrosion Type 3 of 1.2316 Corrosion Resistant Mold Steel: Galvanic Corrosion

Galvanic corrosion occurs when two different metals touch each other. For example, a carbon steel ejector pin fitted on a 1.2316 mold, or a copper electrode inserted into the mold. In wet or acid environments, the more active metal (carbon steel or copper) acts as the anode and gets corroded, while 1.2316 works as the cathode and stays intact. However, if it contacts nickel-based alloy or titanium alloy, 1.2316 will turn into the anode and corrode much faster.

Solutions:

• Use the same metal material as much as possible to avoid contact between different metals.
• If mixed metals are necessary, add insulation layers on touching surfaces.
• Design molds to reduce areas where liquid can gather and stay.

Anti-Corrosion Formula of 1.2316 Corrosion Resistant Mold Steel

The good anti-rust performance of 1.2316 does not come from one single metal element. It relies on the joint work of chromium and molybdenum. 16–18% chromium forms a protective passive film of Cr₂O₃. 0.80–1.30% molybdenum strengthens this film to stop chloride ions from breaking through. This mix works like body armor with extra protective plates. Chromium makes the base layer, and molybdenum acts as the reinforcing layer.

Material Selection Guide: Working Conditions That Require 1.2316 Corrosion Resistant Mold Steel

1. Corrosive plastic materials (PVC/POM/PC with glass fiber / flame retardant ABS): Must choose 1.2316 Corrosion Resistant Mold Steel.
2. High humidity production workshop or coastal factory: Highly recommended.
3. Molds need SPI A1 or higher mirror polish: Must choose it. Regular mold steel keeps tiny holes after polishing that trap corrosive substances easily.