Salt spray tests include exposing coated materials to a continuous, fine saltwater mist in an enclosed, controlled environment. To hasten the corrosion process, the temperature and humidity inside the chamber are kept at predetermined levels. The saltwater mist mimics the corrosive conditions that the PVD coatings may experience in natural settings, such as coastal or industrial settings.
Depending on industry standards, application requirements, or the anticipated service life of the coating, the test's length may change. 1000 hours is a typical benchmark for decorative coatings, while additional time frames might be set to achieve various degrees of corrosion protection.
Evaluation and outcomes
Following the test, the samples are taken out of the chamber, cleaned, and examined for corrosion indicators including discolorations, blistering, delamination, or pitting. To evaluate the effectiveness of the coating, the degree of corrosion damage is compared to predetermined standards or control samples. The outcomes are utilized to assess the PVD coating's appropriateness for the intended decorative application and can be used to inform advancements in coating components, designs, and deposition procedures.
Why is the salt spray test significant?
The salt spray test aids producers and end-users in ensuring that their decorative applications maintain their visual appeal and durability across a variety of weather circumstances. It offers useful insights into the real-world performance of PVD coatings. PVD coatings are a trustworthy option for decorative applications since they successfully pass this test and exhibit a greater level of corrosion resistance.
Owing to their aesthetically pleasing qualities, corrosion resistance, and wear resistance, PVD (Physical Vapour Deposition) decorative coatings are frequently utilized. However, these coatings must overcome several difficulties to last 1000 hours of salt spray testing (a common test technique for assessing corrosion resistance):
1. adherence: A PVD coating must have good substrate adherence to resist salt spray testing. In severe settings, poor adherence can cause the coating to delaminate, peel, or flake.
2. Thickness: The coating's capacity to prevent corrosion on the substrate depends heavily on its thickness. Better barrier qualities are provided by a thicker coating, but the likelihood of cracking or spalling may also rise. To perform at your best, the ideal balance must be struck.
3. Uniformity: For consistent protection, the PVD coating's composition and thickness must be homogeneous. Coatings that are not consistent might have weak places that are more prone to corrosion.
4. Porousness: A porous covering enables the salt and other corrosive substances to pass through and reach the substrate, potentially causing corrosion. To avoid this, PVD coatings must be thick and have minimal porosity.
5. Stability: To withstand challenging environment without compromising chemical composition and microstructure on the surface and in the bulk.
6. Tribological characteristics: To lower the risk of mechanical failure, PVD coatings must retain their microstructure and chemical composition and high wear resistance in corrosive conditions.
7. Proper edge covering is crucial since sharp edges and corners are sometimes more prone to corrosion. On intricate geometry, ensuring uniform coverage might be difficult.
The PVD method must considers several variables, including substrate preparation, process parameters, coating materials, and post-deposition treatments, in order to overcome these difficulties. PVD coatings may be able to withstand 1,000 hours of salt spray testing indicating high corrosion resistance by optimizing these elements.
Picture left to right: Brass polished and PVD coated in Salt Spray Test for 0 h – 24h – 48h
Far right: non coated sample 48 h SST
"Pushing the boundaries: Innovations in PVD coatings that outshine corrosion."
Physical vapor deposition (PVD) coatings have become a well-liked option in surface treatments because of their outstanding fusion of beauty, toughness, and corrosion resistance. Innovative thinkers are looking for innovative methods to improve the performance of PVD coatings in corrosive environments as industries change and consumer demands rise.
Let's examine a few of these ground-breaking innovations:
1 Advanced coating materials: Researchers are developing coatings with enhanced barrier qualities and higher resistance to wear, corrosion, and oxidation by experimenting with innovative materials including multi-layered structures, alloy coatings, or nanoparticles.
2 Optimized process settings can provide coatings that are more homogeneous, dense, and sticky and are resistant to abrasion in severe conditions. Examples of these processes are sputtering and evaporation.
3 Hybrid strategies: By combining PVD coatings with other surface treatments like electroplating, anodizing, or sol-gel techniques, it is possible to produce effects that are synergistic and improve corrosion resistance as well as other performance traits.
4 Adaptive coatings: A cutting-edge strategy for lengthening the lifespan of PVD-coated components is the creation of smart or adaptive coatings that can self-heal, react to environmental stimuli, or release corrosion inhibitors.
The mechanical, tribological, and corrosion-resistant qualities of the coating can be further improved by applying surface treatments such as plasma nitriding, thermal annealing, or ion implantation following PVD deposition.