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Product Technical Solution
Created on 2024.10.18
Star Metal Anti-corrosion Technology Solution
1. Technical Introduction
Workpieces are subjected to a complex environment of high salt spray, high humidity, and tidal fluctuations, posing a huge challenge to the anti-corrosion design of high-strength fasteners. According to national standards, the general anti-corrosion level should reach the standard of C5 or CX. According to the anti-corrosion standard, C5 requires a neutral salt spray ≥2000h, and CX requires a neutral salt spray ≥4000h. Traditional anti-corrosion treatments generally use 100μm hot-dip galvanizing for C5 and 120-150μm hot-dip galvanizing for CX. Currently, some units also adopt the solution of using 304 stainless steel fasteners.
However, in practical use, hot-dip galvanizing has the following issues:
Due to excessive thickness affecting the adhesion to the substrate surface, it is easy to cause problems such as zinc peeling, resulting in a decrease in corrosion resistance.
Due to the soft surface of the zinc layer, excessive thickness affects the bite force between workpieces, especially safety fasteners represented by fasteners. Due to the excessive thickness of the zinc layer, the gap between the teeth increases, causing an imbalance of forces, leading to the failure or even fracture of the fasteners. It is generally believed that the surface coating thickness of fasteners should not exceed 60μm, preferably not exceeding 30μm. Therefore, fasteners treated with hot-dip galvanizing are difficult to meet the requirements of C5. Generally, the neutral salt spray resistance of fasteners with a thickness of 60μm is around 500h. To avoid excessive coating, generally, nuts with internal threads do not have a hot-dip galvanized coating.
Due to the easy reaction of the zinc layer surface with oxygen to generate sponge-like zinc oxide (white rust), it is prone to moisture absorption in marine environments, accelerating the subsequent corrosion of the substrate. At the same time, white rust can also cause difficulties in disassembly and assembly of fasteners and other connecting components, affecting subsequent maintenance.
At the same time, special processes are required for hot-dip galvanized coatings of 100μm and above. It is generally difficult to achieve uniform thickness, reach a single point of ≥100μm, and zinc accumulation is prone to occur. At the same time, the phenomenon of substituting inferior goods for superior ones is also likely to occur.
During the production process, problems such as wastewater, waste acid, and zinc vapor pollution will be generated.
At the same time, there are the following problems with stainless steel fasteners in actual use:
Due to the much lower mechanical properties of stainless steel compared to alloy steel, the phenomenon of failure due to insufficient mechanical properties of fasteners is prone to occur at critical points.
The general 304 stainless steel fasteners can generally withstand neutral salt spray for about 400 hours. In particular, the phenomenon of substituting inferior goods for superior ones sometimes occurs, and red rust appears on some 304 fasteners after 200 hours of neutral salt spray.
Stainless steel fasteners are prone to deformation, causing the fasteners to seize up, which is inconvenient for later maintenance.
4. Stainless steel prices are relatively high, especially greatly influenced by international nickel prices.
To solve the above problems, our company has introduced a composite anti-corrosion technology combining gas permeation and modified coatings, which has several major advantages compared to traditional techniques:
Corrosion resistance neutral salt spray ≥4000h, meeting the corrosion resistance standard of CX.
Due to the composite anti-corrosion process of infiltration layer and coating layer, the neutral salt spray is ≥1000h when the surface coating is damaged. Testing has shown that maintenance intervals can be extended from once a month to every three months to six months, greatly reducing maintenance costs.
The coating thickness is 15-20μm, which also improves the surface hardness and fatigue resistance of the substrate, greatly enhancing the structural stability.
Our technology provides at least a 4 times improvement in anti-corrosion performance compared to hot-dip galvanizing, with only a doubling in price. This offers a significant cost advantage compared to stainless steel fasteners, and most importantly, greatly reduces maintenance costs in the long term.
Our technology has successfully passed the evaluation organized by the China Surface Engineering Association, with Academician Han Buxing as the leader of the expert group, and the evaluation is rated as internationally advanced.
Two, technical solution
Fasteners solutions for photovoltaic and wind power applications
Anticorrosion technology | Neutral salt spray corrosion Experiment (hours) | Copper salts accelerate corrosion Experiment (hours) | The binding force with the matrix | Whether to improve matrix mechanical performance | Environmental pollutants | Rough prices (specifically subject to change based on model) |
Hot-dip galvanized (60μm) | 500 | Sixty | Excellent | 否 -> No | Pickling, plating solution | 10000 |
MSG2000: The message could not be delivered. | 2000 | 200 | Excellent | is | Without | twenty thousand |
MSG4000 | 4000 translates to "four thousand" in English. | 400 | excellent | is | Without | 30,000 |
C5 adopts the MSG2000 scheme, and CX adopts the MSG4000 scheme. Specific technical specifications are as follows:
Product Salt Spray Comparison:
60μm hot-dip galvanized nut neutral salt spray 480h | 304 stainless steel neutral salt spray 240h |
304 stainless steel neutral salt spray 480h | MSG2000 nut neutral salt spray 480h |
MSG2000 nut neutral salt spray 2160h | MSG2000 nut neutral salt spray 3600h |
MSG4000 nut neutral salt spray 2160h | MSG4000 nut neutral salt spray 4160h |
Performance comparison table of high-strength corrosion-resistant fasteners and stainless steel fasteners (M12)
304（A2-70） translates to "A2-70" in English. | 304（A2-80） translates to "Not Found" in English. | 35CrMo(星科) translates to 35CrMo (Xingke) in English. | XK10 |
|
Tensile strength (MPa) | 700 | 800 | 1083 translates to "one thousand and eighty-three" in English. | 1221 |
Yield strength (MPa) | 450 | 600 | 1079 | 1137 |
Hardness HRC | fourteen | fourteen | twenty-two | thirty-five |
Fracture growth rate% | forty | forty | 15 | Fourteen |
Cross-sectional shrinkage rate% | Sixty | Sixty | Fifty-eight | forty-eight |
Neutral Salt Spray (NSS) | 400 | 400 | 2000 | 4000 translates to "four thousand" in English. |
Price (yuan/ton) | 24,000 | 250000 (excluding domestic products) | twenty thousand | forty thousand |
Maintenance Plan
Our company has specially developed graphene epoxy zinc-rich self-spraying paint for later maintenance. Due to the surface coating damage of our company's technology, it can withstand neutral salt spray for more than 1000 hours. Generally, spraying graphene epoxy zinc-rich self-spraying paint on the exposed bottom part can achieve the purpose. This paint can withstand neutral salt spray for more than 800 hours with a single layer. If there are very few rust spots, use a portable laser rust remover to remove the rust spots and spray with graphene epoxy zinc-rich self-spraying paint.