The Science Behind Preventing Rust and Corrosion in Molds
Rust never sleeps. That’s an unfortunate truth for manufacturers in the plastic molding industry. While your molds are hard at work, churning out part after part, an invisible enemy is constantly waging war.
Corrosion impacts your bottom line through costly downtime, frequent mold repairs and replacements, and product quality issues. Every minute a corroded mold is out of commission, it is missed production and revenue down the drain.
The high stakes make preventing rust and corrosion critical for molders looking to stay competitive. Luckily, understanding what feeds this nemesis – the underlying chemical processes – is half the battle. Once you know the science behind corrosion, you can implement targeted prevention strategies to defend your most valuable production assets.
Understanding Rust and Corrosion in Injection Molds
Rust and corrosion are terms often used interchangeably but represent distinct chemical processes. While rust specifically refers to the reddish-brown flaking on iron and steel caused by oxidation, corrosion encompasses a broader range of chemical reactions that degrade materials like metals, plastics, and ceramics.
Let’s start with rust – which forms when iron combines with water and oxygen in an electrochemical process. As the iron loses electrons, it forms iron oxides that weaken the metal’s structure. Rust directly compromises a mold’s integrity and performance over time.
Corrosion attacks various materials through similar electrochemical reactions with their environments. While rust is specific to iron-based metals, corrosion can degrade non-metallic components critical to mold operation. The rate and extent of corrosion depend on factors like water chemistry, pH levels, and even the material’s composition.
Factors Influencing Corrosion Rates in Injection Molding
Not all metals face corrosion at the same pace. Whether rust takes over quickly or is held at bay depends on environmental conditions and the metal’s inherent properties.
Environmental Influences
- Humidity enables corrosion by providing moisture that forms a conductive film on metal surfaces, facilitating electrochemical reactions that lead to rust. In environments with humidity above 60%, metals are more susceptible to corrosion.
- Higher temperatures increase the rate of the chemical reactions driving corrosion. As heat intensifies molecular mobility and kinetic energy, oxidation accelerates. Manufacturing equipment operating at elevated temperatures requires diligent corrosion management.
- Dissolved salts make moisture significantly more corrosive. Salts from salty sea air or industrial processes reduce water’s electrical resistance, allowing aggressive pitting corrosion. Components exposed to salts face an elevated corrosion risk.
Metal’s Inherent Resistance
- Some alloys are engineered to be more corrosion-resistant. They either contain metals that act as a sacrificial anode and corrode before the primary metal or form a thin, protective oxide layer on the surface that acts as a barrier against corrosion attacking the underlying metal.
- Mold surfaces that are smooth and polished provide fewer areas for corrosion to begin. In contrast, rough, uneven surfaces allow moisture and contaminants to collect in crevices and initiate corrosion more easily. Surface treatments like plating, paint, and anodizing add a protective barrier.
For molders, strategic material selection and accounting for operating conditions during design are vital to avoiding accelerated degradation that disrupts production. Proper planning allows you to manage this chemical threat to your critical molding assets effectively.
Corrosion Types Relevant to Molds
Corrosion takes on many different forms, each with its own attack mechanism and consequences. Gaining familiarity with these various types of corrosion is key for manufacturers looking to protect their vital molding assets and maintain consistent operations.
- Uniform corrosion degrades a mold’s surface evenly over time. This steady material loss can alter critical dimensions and tolerances, affecting part quality as the mold wears down.
- Galvanic corrosion occurs when dissimilar metals are joined in a mold, such as aluminum and steel sections. When exposed to an electrolyte, one metal corrodes preferentially where it meets, potentially compromising structural integrity.
- Pitting corrosion creates small but deep holes that perforate the surface. These pits can disrupt the mold’s finish and allow leakage paths that ruin parts despite being hard to detect.
- Crevice corrosion occurs in narrow, sheltered spaces like underneath gaskets where stagnant electrolytes accumulate out of sight. This hidden damage can undermine the mold’s precision from within.
- Stress corrosion cracking occurs when tensile stress and a corrosive environment combine to cause cracks that can lead to catastrophic failure in susceptible alloy molds exposed to high heat and stress.
- Intergranular corrosion attacks the grain boundaries of metals while leaving the grains relatively untouched, which can affect improperly heat-treated stainless steel molds exposed to substances that target those boundaries.
- Environmental factors like acidic or basic conditions, harmful production chemicals, and plastic material residues containing aggressive additives can accelerate the general corrosion of injection molds.
Potential Mold Corrosion Sites
Even advanced molds have areas more susceptible to corrosion that require attention:
- Welded sections are vulnerable, as the weld material and surrounding heat-affected zones often have different corrosion resistance than the base metal.
- More complex geometries with intricate cooling channels, tight radii, or minuscule part details provide more spaces for crevice and pitting corrosion to initiate. These areas are difficult to maintain properly.
It’s crucial to maintain both the interior and exterior of the mold, including the sprue bushings. Rust in these areas can compromise the nozzle seal and overall mold integrity. Applying a protective coating can prevent such issues. Moreover, rust at the clamp points can affect mold alignment, potentially requiring increased clamp pressure or causing product defects. Regular maintenance and protection are key to avoiding these problems.
Rust and Corrosion Prevention Methods in Injection Molding
Understanding and implementing corrosion prevention strategies is key to maintaining efficiency in injection molding and precision tooling operations. These are practical steps for corrosion protection, including cutting-edge surface treatments and corrosion inhibitors.
1. Material Selection
Choosing the right material for the mold is the first line of defense against corrosion. Although more expensive, stainless steel is often preferred for its resistance to rust and corrosion. Other materials can be treated or coated to enhance their corrosion resistance.
2. Protective Coatings and Surface Treatments
Protective coatings or surface treatments can significantly increase a mold’s resistance to corrosion. These can include:
- Chromate conversion coatings for aluminum molds to improve corrosion resistance.
- Nickel plating or chrome plating for high wear and corrosion resistance.
- Anodizing for aluminum parts enhances surface hardness and corrosion resistance.
- Nanocoatings provide a barrier against moisture, chemicals, and wear.
Nanoplas offers a range of high-performance coatings and products designed to protect molds from corrosion and facilitate easier mold release and cleaning.
3. Use of Corrosion Inhibitors
Corrosion inhibitors can be used to prevent rust formation. These chemicals form a protective layer on the surface of the metal, significantly reducing the oxidation process that leads to rust.
4. Environmental Control
Controlling the environment around the injection molding machine and the storage of molds is vital. This includes:
- Dehumidification to reduce moisture in the air.
- Temperature control to avoid condensation.
- Cleanliness to prevent the buildup of corrosive substances.
5. Regular Maintenance and Cleaning
Regular maintenance and cleaning of molds are essential to remove any residues that could cause corrosion. This includes periodic inspections for early detection of rust or corrosion and immediate action to address any issues. Nanoplas’s Zap-Ox cleaner effectively removes rust, oxidation, buildup, weld discoloration, and other stains, reducing downtime.
6. Proper Storage
When molds are not in use, it’s important to store them in a controlled environment to shield them from dust and moisture. A modern approach to mold protection involves applying a dry film coating, which adheres to the mold surface without affecting existing lubricants. A dry rust preventative does not compromise the grease or other lubricants present, ensuring the mold’s smooth operation. Furthermore, it offers acid-neutralization properties, protecting against corrosion from fingerprints and residue. Nanoplas provides advanced rust-preventative solutions that are effective on both cold and warm molds, ensuring comprehensive protection regardless of the mold’s operational temperature. These measures significantly enhance the longevity and reliability of stored molds.
Maximize Mold Life with NanoPlas Rust and Corrosion Preventatives
Nanoplas’s line of rust preventatives goes on completely “dry” to reduce scrap and downtime spent cleaning the mold before start-up. These products are specifically formulated to protect the mold and improve its operational efficiency, ensuring that the quality of the parts remains consistently high. Creating an easily cleanable, corrosion-resistant surface extends mold longevity, enhances efficiency, and ensures consistent part quality.
You can significantly enhance mold longevity and reliability by selecting the right materials, enforcing regular inspections and maintenance, utilizing advanced protective technologies, and controlling environmental factors. The key is prioritizing diligent prevention efforts, sharp detection methods, and rapid response – ensuring your operations stay productive while meeting quality standards.
Preventing rust and corrosion requires ongoing vigilance, innovation, and deep technical understanding. The tools and strategies available, particularly those from leaders like Nanoplas, offer a path to success.
Experience Nanoplas’s complete line of mold maintenance products by ordering your free sample today.
