304/316 K2-K6 high salt spray plastic special fast thread self-tapping screw is a fastener designed for high corrosion environment, such as coastal, chemical and plastic substrate, combining specific stainless steel material, salt spray protection process and fast thread structure. The following summarizes its core functions.
The first element of performance is material. Let's talk about the core difference between its two main materials-304 and 316 stainless steel.
304 stainless steel: contains 18% chromium and 8% nickel, forming a basic passivation film, providing medium corrosion resistance. It can meet the needs in a generally humid environment, but pitting is prone to occur in high chloride ion environments (such as coastal and chemical areas). Without strengthening treatment, the salt spray test is usually 48~96 hours; after passivation treatment, it can reach 240~500 hours.
316 stainless steel: adding 2%~3% molybdenum significantly improves resistance to chlorides and acidic media, suitable for high corrosion scenes such as marine and medical. After passivation, the product can last for more than 1,000 hours, which is about 60% more than 304, but the service life is extended by 3 to 5 times.
The K series (K2-K6) is optimized for plastic properties to solve the problems of easy cracking and thread slipping of traditional screws. Let's talk about the threads and structures of the K series.
Thread design innovation
High-low thread structure: K2/K3 uses double-lead thread - high thread has less resistance when cutting into plastic; low thread provides a larger bearing surface, improves the pull-out strength by more than 30%, and reduces the risk of internal stress cracking.
Wide pitch (PT thread): K4 and K5 use 48° thread angle and sparse pitch to avoid excessive extrusion of brittle plastics. PVC and acrylic are common plastic materials in life.
Self-drilling ability: K6 and other models are equipped with a three-blade drill tail or cross blade, which can penetrate glass fiber reinforced plastics without pre-drilling, which can save 50% of process time.
Chip control: The cutting groove design guides the discharge of chips to prevent the hole from clogging and causing torque surge.
A three-level protection system is designed for high salt spray environments.
Surface passivation technology: Nitric acid or electrolytic passivation is used to form a dense chromium oxide film on the surface, and the salt spray time is increased from 96 hours to 500 hours (304 material) or 1000 hours (316 material).
Plating reinforcement (optional) Black stainless steel screws are treated with carbonitriding, and the surface hardness reaches HV800, while taking into account corrosion resistance and wear resistance.
Sealing structure: Some K series have integrated rubber rings at the root of the thread to block salt water from penetrating into the gap, which meets C4/C5 anti-corrosion certification.
Product selection suggestions: Pursue a cost-effective 304 + K2 or K3 combination, suitable for indoor or low-salinity environment home appliances, and toy assembly.
Must-have for extreme environments: "316 + K5/K6" is the golden solution for marine and chemical scenes. Although the cost is high, the maintenance cost of the whole life cycle is lower.
Failure prevention: Avoid using it at high temperatures above 400℃ (the tensile strength of 316 material decreases by 5% for every 100℃ rise after exceeding 100℃)
The above is an introduction to the core functions of this product. If you also have product needs, please let us know.
