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The natural environment spectrum and equivalent conversion relationship are important input parameters for the complication of aircraft acceleration test environment spectrum. Due to the large discrete nature of environmental data and the small number of sample data, traditional parameter estimation methods are no longer suitable for compilation of natural environment spectra. Based on the idea of small sample parameter estimation, this paper established a high confidence natural environment spectrum through Bootstrap data expansion and grey confidence interval estimation. Subsequently, electrochemical tests were carried out on 7050 aluminum alloy and TC18 titanium alloy, which were typical dissimilar metal connection materials for aircraft, and their equivalent conversion coefficients were calculated at the temperature of accelerated test environment based on the principle of isoelectric quantity. On this basis, the accelerated test environment spectrum of aluminum-titanium alloy joint structure was given, which could provide a reference for the engineering of calendar life assessment of aircraft dissimilar metal joint structure.

Taking X100 and X80 pipeline steels as research objects，their stress-strain curves in air and under different applied potentials were obtained through the slow strain rate tensile test (SSRT).The stress corrosion sensitivity analysis showed that the applied potential had a significant effect on the SCC sensitivity and corrosion cracking mechanism of X100 and X80 pipeline steels in 3.5%NaCl neutral solution.Under the same stress corrosion conditions，the SCC sensitivity of X100 pipeline steel was lower than that of X80 pipeline steel.The characteristics and differences of the corrosion resistance of X100 and X80 pipeline steels were analyzed by combing the observation of fracture morphology and fast/slow scan tests of polarization curves，the stress corrosion mechanism type of X100 and X80 pipeline steel materials under different applied potential conditions could be obtained，when the applied potential was higher than -395 mV，the metal was in the state of activation dissolution；when the applied potential was -395～-462 mV(X80 steel) or -395～-504 mV(X100 steel)，the mechanisms were membrane crackinganodic dissolution(AD) and hydrogen induced crack.If the applied potential further decreased，the mechanism was hydrogen induced crack.

The resistivity of the anti-corrosion coating of buried steel pipeline is an important parameter.In recent years，the value of this parameter has been used to evaluate the overall quality of the anti-corrosion coating of in-service or directional drilling pipelines.All the domestic standards regarding the on-site measurement of this parameter and the evaluation of the overall quality of the anti-corrosion coating are established with reference to NACE TM 0102-2002.However，those domestic standards have not explained the concept of "anti-corrosion coating resistivity" clearly and there is confusion with terms related to "anti-corrosion coating resistivity".The reasons for selecting the general method and the attenuation method are not defined clearly for the measurement of the resistivity of anti-corrosion coating in various standards，and the test location of the soil resistance is not specified when the general method is used for the directional drilling crossing pipeline，resulting in differences in the field test results and evaluation conclusions of the resistivity of the anti-corrosion coating outside the same pipeline by various inspection units.In order to clarify the above problems，the concepts related to the resistivity of the anti-corrosion coating were explained firstly，and then the meaning of the resistivity of the anti-corrosion coating was clarified through theoretical analysis and formula derivation.Furthermore，the measurement results of the resistivity of the anti-corrosion coating of 100 directional drilling crossing pipelines were statistically analyzed.Finally，suggestions on the revision of relevant standards were given，with expect to revise the unclear problems in the new version of the standards.

In order to study the effect of pre - oxidation treatment on the quality of the nitriding layer of stainless steel parts, quenched and tempered samples were treated with different pre - oxidation and sand blowing treatments before nitriding. The color of the preoxidized film was observed visually. The microstructure, depth, hardness, and brittleness of nitriding layer were measured by metallographic microscope and hardness tester. Results showed that the passivation film on the surface of 1Cr11Ni2W2MoV stainless steel could be destroyed if the steel was preoxidized at 550 ℃ for 5～20 min before nitriding. So the hardness, depth and structure of the nitriding layer could meet the technical requirements for nitriding if treated so. Furthermore, the uniformity and nitriding speed of the layer were better than that of the layer with only sand blowing treatment before nitriding.