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弹簧表面处理后进行质量检验，主要包括外观检验、耐腐蚀性能检验、保护层结合力检验和氢脆检验，必要时还应检验保护层厚度。
每种型号的弹簧，根据其使用条件和不同的表面处理方法，都会进行上述检查项目。一般情况下，检查项目和方法在零件产品图样或相应的技术标准中有规定。
- 外观检查
Appearance inspection is the most basic and most commonly used inspection item. Springs with unqualified surface treatment and appearance do not need to undergo the following inspection items.
After surface treatment, the spring should be bright and beautiful, with normal color, without defects such as deposits, spots, bubbles, shedding, deep scratches, and yin and yang surfaces. However, minor defects that do not damage the appearance and do not reduce the corrosion resistance (such as saponification or passivation liquid marks, etc.) are allowed.
Before oiling (or varnishing) oxidation and phosphating treatment, the appearance of the oxide film and phosphating film should be inspected. After oiling (or varnishing), it is also necessary to inspect the appearance of the finished product.
Based on appearance and surface quality, springs can be classified as qualified, repaired, and scrap. Repaired springs require the removal of the unqualified protective layer and reprocessing. However, springs that have been repeatedly repaired and failed or are excessively corroded must be scrapped.
（2）Corrosion Resistance Test
The corrosion resistance test of springs is the most important test item for the quality of spring surface treatment. Currently, the most commonly used test item for spring products is the neutral salt spray test. The salt spray test can be applied to springs with various surface treatment methods. The specific method is: conduct it according to the requirements of GB/T 10125-2012. After the salt spray test, the coating is divided into four grades according to the time it takes for red rust to appear on the coating, ranging from 120 to 1000 hours.
However, salt spray testing requires a relatively long test cycle, so there are relatively quick test methods for evaluating the corrosion resistance of spring surfaces, primarily the immersion method and the drip method.
The drip method typically uses a 2% copper sulfate solution. During testing, clean the spring surface with alcohol. Several drops of copper sulfate solution are added while a stopwatch is run. A spring is considered acceptable if no copper spots appear on the oxide film (blackening) after 20 seconds, and if no copper spots appear on the phosphate film after more than 3 minutes.
The soaking solution is generally a 2% copper sulfate solution or a 3% salt solution.For oxide film, soak it in a 2% copper sulfate solution at room temperature for 20 seconds, then remove it and rinse the surface with water. If there is no red contact point, it is qualified. If it is soaked in a 3% salt solution for 15 minutes, remove it and it is qualified if there is no rust.
For phosphate coatings, soak the spring in a 2% copper sulfate solution. After holding at room temperature for 3 minutes, remove the spring and rinse the surface with water. If there are no red contact spots, the spring passes. If soaked in a 3% salt solution for 2 hours, remove the spring and if there are no rust marks, the spring passes. Alternatively, soak the spring in a 3% salt solution for 15 minutes, then remove and rinse with water. Allow the spring to air dry for 30 minutes. If no yellow rust appears, the spring passes.
In addition to the conventional inspection methods mentioned above, since automobiles and mechanical products that use a large number of springs have relatively high quality requirements for springs, some large multinational companies have special test items for some important springs, such as damp heat tests (tests under specified temperature and humidity conditions), cyclic corrosion tests (tests under periodic cyclic conditions of temperature, humidity and salt spray), and gravel impact tests (for automobile suspension springs with higher requirements). Spring manufacturers need to equip themselves with corresponding testing equipment and technical capabilities according to user needs.
（3）Adhesion test
The adhesion of the protective layer (also known as bonding strength) refers to the degree of firmness of the bonding between the coating or coating and the substrate or intermediate layer, also known as the adhesion test.
There are also various test methods for testing adhesion. For non-electrolytic zinc-rich metal coatings, there are the tape test (according to GB/T 5270-2005) and the cross-cut method (see Section 4.3 of this chapter). There are also the following test methods:
1) Coating Adhesion Test: After treating the spring at 220°C for 30 minutes, immediately place it in room temperature water. If the coating shows no blistering or cracking, the test is acceptable.
2) For springs with smaller diameters, use the same steel wire as the spring and sample the surface along the groove. For diameters d < 1mm, wrap the steel wire sample around a shaft that is three times the diameter (= 3d). For diameters d ≥ 1mm, wrap the copper wire sample around a shaft of the same diameter, completing 5-10 turns. No peeling or shedding should occur.
3) For springs with larger diameters, use a file to file along the protective coating at a 45° angle, or use a steel needle (or blade) to cross-cut the coating and observe for peeling or shedding at the intersections or filing points. 4) For galvanized or chrome-plated springs, to determine the bonding strength of the coating, sample the spring and heat it in a resistance furnace to 180-200°C for 1 hour to see if the coating bulges or falls off.
(4) Hydrogen embrittlement test
弹簧材料强度很高，成形时变形剧烈，因此对氢脆特别敏感（特别是小型螺旋弹簧或曲率半径较小的板簧）。实际生产中，常常有大量弹簧因氢脆而报废。
检查弹簧是否氢脆的方法相对简单。对于螺旋弹簧，施加适当强度的压缩（或拉伸，或扭转）载荷。对于板簧，根据具体情况施加力和变形。经过一段时间（例如24小时）后，观察是否有裂纹或断裂。如果弹簧断裂，用虎钳夹住断裂的弹簧，用钳子抓住突出部分，用力弯曲。氢脆弹簧通常在45°至90°的弯曲角度内以非常脆的方式断裂。
- 镀层（涂层）厚度检测
为保证防护层的耐腐蚀性能，镀（涂）层应有足够的厚度。镀层厚度可以用千分尺、塞规、螺纹环规等检查，也可以用化学方法或金相方法测量。
检查涂层厚度的化学方法通常是滴加法。测量时，用移液器将溶液滴到测量区域。溶液停留1分钟后，用棉球擦去。然后再滴加一滴，直至露出基底金属。最后，根据滴数计算涂层厚度。