Real laboratory data on stainless steels (1.4310, 1.4568) and eight anti-corrosion coatings against six corrosive media: seawater, 40% MgCl₂, 3% NaCl, 0.1N NaOH, 0.1M citric acid and deionized water. Four test blocks — unstressed, stressed, fatigued and VDA cyclic test — to reflect real working conditions.
Disc springs typically work under high loads and, in many sectors, in the presence of moisture, salt-laden atmospheres, acids, cleaning agents or seawater.
The combination of mechanical stress + corrosive agent + temperature + fatigue is what determines the spring's real service life.
The behavior of a disc spring against corrosion changes drastically depending on its load state and environmental exposure. That is why the tests have been organized into four blocks that reproduce the four real working scenarios of the spring.
In international technical terminology, these are known as corrosion tests on disc springs (also Belleville washers corrosion testing), and they include immersion tests, stress corrosion cracking tests and corrosion fatigue tests.
Each block measures a different metric · Direct access to each one
Reveals the intrinsic behavior of the material or coating against the corrosive agent, with no influence from internal stresses. It is the cleanest test for comparing materials and protections.
Introduces the stress corrosion cracking (SCC) factor. Under load, certain stainless steels can fracture even in media where the material on its own performs well.
Combines corrosion with the cyclic wear that locally destroys the passive layer, opening up zones of accelerated electrochemical corrosion. Reflects springs in dynamic applications.
Accelerated test in a climatic chamber combining salt spray, high humidity and drying at alternating temperatures. Recognized as an automotive benchmark — it complements the immersion tests when you want to correlate with outdoor service life or marine atmospheres.
The test methods used aim to cover the spectrum of conditions that can affect a disc spring in service.
Combining temperature, stress state and corrosive medium, the possible scenarios are almost unlimited: corrosion does not affect a part deflected to 10% of its travel the same way as one at 80%, nor does an environment at 40 °C behave like one at 80 °C. For this reason, a set of tests with the broadest and most representative combination of factors possible has been selected.
The VDA test is included, for its recognition as a benchmark, as a complement to the unstressed immersion tests — for which no standard exists. The immersion tests run for 4 weeks with no contact with the environment. The specific details of each test are spelled out in its own block.
The samples, dimensions, materials and coatings are consistent across all four blocks, which allows a direct comparison of the effect of adding stress, fatigue or climatic cycles to the same spring exposed to the same medium. All geometries comply with DIN 2093 / DIN EN 16983; the stainless steels are manufactured by stamping and grinding, and the coatings are applied on standard 51CrV4 spring steel.
| Dimensions Do × Di × h × t (mm) | Standard | Series |
|---|---|---|
| 63 × 31 × 1,9 × 4,5 | DIN 2093 | C |
| 80 × 41 × 3,0 × 5,3 | DIN 2093 | B |
| 63 × 31 × 1.8 × 4.15 | DIN 2093 | C var. |
Stainless steels tested
Standard austenitic stainless steel
Shot peened for fatigue resistance
Precipitation hardened
Shot peened + 17-7 PH
Carbon diffusion — wear resistance
Coatings tested (on 51CrV4)
Mechanical zinc plating + yellow chromate
Mechanical zinc plating + clear chromate
Zinc-aluminum flakes
Hexavalent chromium-free · Dacromet successor
Zinc base + polymer topcoat
Electroless nickel plating
Water-based organic coating
Storage protection only
See the technical description of the base materials and the anti-corrosion coatings for detailed information.
Corrosive media
53.5% salt · pH 7.8–8.2
Offshore · marine
Extreme chloride concentration
Standard for SCC in stainless steels
3% aqueous solution
Automotive · de-icing salts
Alkaline solution · pH > 10
CIP cleaning · chemical
Weak organic acid
Food · cleaning
Accelerated salt spray
Marine atmospheric
No aggressive chemistry
Isolate pure fatigue
Procedure by block
The results are indicative. They reflect exactly the test conditions (geometry, material, coating, medium, temperature, load, cycle). In a real application, variations in any of these factors can change the behavior. To size a specific case, we recommend contacting the engineering department to validate the choice of material and protection before manufacturing.
Tell us your use case and our engineering team will advise you on choosing the optimal solution.
Each block measures a different metric — visual scale, hours, cycles or post-chamber appearance — but all four can be cross-referenced to make decisions. The following findings are the most relevant for designing springs under corrosion.
If the application combines several factors (load + chlorides, acid + fatigue, outdoor exposure, etc.), it is best to choose the material/coating based on all four blocks at once, not just the free-immersion one.
| Block | What it measures | Result metric | Access |
|---|---|---|---|
| Unstressed | Intrinsic resistance of the material/coating | Visual scale G / M / P / VP after 4 weeks | View block 01 → |
| Stressed | Service life under constant load in a corrosive medium | Hours to fracture (limit 2,500 h) | View block 02 → |
| Fatigued | Service life under compression cycles in a corrosive medium | Number of cycles to fracture | View block 03 → |
| VDA test | Resistance to accelerated climatic cycles (salt spray + humidity) | Visual inspection · Δ coating after 6 weeks | View block 04 → |
The best stainless steel or coating depends on the medium, the temperature and the load state. There are counterintuitive combinations: oiling, poor in free immersion, is acceptable under load.
Rapid fracture even in 1.4310 and 1.4568 — between 140 h and 1,968 h at 80 °C. It is the international standard medium for evaluating SCC in austenitic steels.
Zinc reacts directly with the acid and dissolves. Galvanized finishes, Dacromet and Geomet fail in short timeframes. In those environments: stainless steel.
Both stainless steels and most coatings withstand > 2,500 h without fracture. Protective oxide/hydroxide layers form.
The residual compressive stresses delay crack nucleation — a clear improvement in the 20-80% and 20-60% tests. It is not an anti-corrosion protection in itself.
The test data applies to the design of disc springs in sectors where the corrosion + load combination is common. If the application combines several factors, it is best to choose the material/coating based on all four blocks at once, not just the free-immersion one.
De-icing salts (NaCl) · coastal salt-laden atmospheres · brake fluids or coolants.
Seawater · flange joints under permanent preload · offshore environments.
CIP cleaning with NaOH · acidic products in process lines.
Citric acid as an ingredient or cleaner · NaOH in sanitization.
Turbines · safety valves · control systems under fatigue.
Pre-tensioned anchors exposed to urban, marine or industrial atmospheres.
It depends on the application. If the spring will work free or with very little preload in a corrosive environment (storage or intermittent use), the unstressed test is representative. If it will be permanently or cyclically compressed, the stressed test is essential: under load, stress corrosion cracking (SCC) phenomena appear that are not seen in free immersion. We recommend always reviewing the block that reproduces the real load state.
Shot peening introduces residual surface compressive stresses that hinder the nucleation and propagation of fatigue cracks — hence the improvement in the cyclic tests. However, it provides no chemical protection against corrosion: it deposits no protective layer and can increase surface roughness, increasing the area exposed to attack. In the unstressed and static-stress tests, shot peening offers no advantage over the untreated material.
In a marine atmosphere (humidity + chlorides), Geomet and Delta Tone + Delta Seal offer the best protection/cost ratio on 51CrV4 base steel: they withstand salt spray and immersion in NaCl without significant degradation over the 4 weeks of testing. For springs under permanent preload in direct contact with seawater, the 1.4310 and 1.4568 steels are the most robust alternative — especially if the design requires resistance to stress corrosion cracking (SCC).
Accelerated tests are valid for comparing the relative behavior of materials and coatings under controlled conditions. Extrapolating to real service life requires knowing the equivalence factor between the test and the service conditions, which varies depending on the dominant mechanism. These results are interpreted as ranking indicators, not as predictors of service life. To size with confidence, we recommend combining them with field experience under similar conditions.
Not as a certification. If your application requires regulatory compliance (NACE MR0175, ISO 15156, EFC, or similar), you need an accredited test to the specific standard. These blocks are designed to guide the selection of material and coating before the certification phase. Our engineers can advise you on which standard applies in your sector and how to interpret the results in that context.
Tell us your use case and our engineering team will advise you on choosing the optimal solution.
