Salt Spray Test Chamber For Automotive Testing

With the rapid development of national industry, technology and economy, the application range of industrial products is more and more wide. In order to ensure the quality and life of the product, many industrial products need to be verified by salt spray corrosion tests, especially automotive products. In recent years, the demand for salt spray testing has been increasing, and many practitioners are confused about how to conduct salt spray testing, how to improve the efficiency of the test and how to choose the standard of salt spray testing. Therefore, this paper systematically introduces what is salt spray test; Types of salt spray tests; Especially, the application of salt spray corrosion test in automobile industry is introduced.

Introduction

Due to the presence of salt spray in the natural environment, salt spray corrosion is one of the most common and destructive atmospheric corrosion. The chloride ions in the salt spray will penetrate the oxide layer and protective layer on the surface of the metal material, and have an electrochemical reaction with the internal metal, thereby destroying the surface of the metal material and its properties, and then further affect and damage the product through the pores and cracks on the metal surface.
Salt spray test is a laboratory simulation of atmospheric salt spray in the environment, which has the characteristics of standardization and acceleration. Compared with the natural environment, the salt concentration of chloride in the salt spray test equipment is usually several times or even dozens of times the salt spray content in the natural environment. Therefore, the corrosion rate is greatly improved, and the corrosion state of salt spray exposed to natural environment for 1 year can be completed in 24 hours under artificial simulated salt spray test environmental conditions, and accurate results can be obtained

Types of salt spray tests

Neutral salt spray test

Neutral salt spray test (NSS test) is the earliest and most widely used accelerated corrosion test method. It uses 5% sodium chloride brine solution, the solution PH adjusted to the neutral range (6.5-7.2) as a spray solution. The test temperature is 35℃, and the salt spray sedimentation rate is required to be 1~2mL/80cm/h.

Acetate spray test

The acetate spray test (ASS test) was developed on the basis of the neutral salt spray test. Is to add some glacial acetic acid to 5% sodium chloride solution, so that the pH value of the solution is reduced to about 3, the solution becomes acidic, and finally the salt spray formed by the neutral salt spray becomes acidic. The corrosion rate is about 3 times faster than the NSS test.

Copper salt accelerated acetate salt spray test

Copper accelerated acetate spray test (CASS test) is a recently developed rapid salt spray corrosion test. The test temperature is 50℃. Adding a small amount of copper salt - copper chloride in salt solution can strongly induce corrosion. The corrosion rate is about 8 times that of NSS test.

Alternating salt spray test

Alternating salt spray test is a comprehensive salt spray test, that is, salt spray, dry, wet and hot (soaking, wet and condensation, etc.) test conditions are combined and cycled to simulate the actual application environment of the product. Through the penetration of the tidal environment, the salt spray corrosion not only occurs on the surface of the product, but also occurs inside the product.
 

Test method item	Neutral salt spray（NSS）	Acetate spray（ASS）	Copper salt accelerated acetate salt spray（CASS）
temperature	35C+/-2C	35C+/-2C	50C+/-2C
Average settlement	15ML/H+/-0.5ML/H	15ML/H+/-0.5ML/H	15ML/H+/-0.5ML/H
Sodium chloride concentration	50g/L+/-5g/L	50g/L+/-5g/L	50g/L+/-5g/L
PH	6.5 to 7.2	3.1 to 3.3	3.1 to 3.3

Standard method for circulating salt spray for automotive materials

The automotive industry is one of the first industries to use cyclic salt spray test as a means of evaluating product reliability. Basically, major automobile manufacturers have their own cyclic salt spray test standards, mainly the following types.

1. CCT cycle

This method is currently recognized by the industry, mainly used for the detection of automotive steel plates and parts, CTT cycle on the basis of neutral salt spray method, adding drying and wet heat two links, after many optimization and improvement, has been developed to CCT IV, and has been cited in ASTM D 6899-2003 standard method. The humid and hot conditions are 60℃, 95%, for 75 minutes, the drying temperature and humidity are lower than 60℃, 30%, for 160 minutes, and then go through the humid and hot stage again.

2. GMW 14872

GMW 14872 Cyclic Corrosion Laboratory is a standard method of cyclic salt spray test developed by General Motors in the United States, which is characterized by the combination of wet heat and dry superimposed storage environment. That is, the cyclic cycle test of ambient temperature (25 ℃, 45%RH) 8h→ humid heat (49℃, < 100%RH) 8h→ dry (60 ℃, ≤ 30%RH) 8h, in addition to salt spray, in the ambient temperature stage, other environmental factors can also be added, such as gravel, dust, thermal shock, mechanical shock, etc. Select different cycle times according to many different body positions such as underbody parts, engine compartment parts, external parts and internal parts.

3.SAE J2334

SAE J2334 Laboratory Cyclic Conosion Test is a standard method for cyclic salt spray test developed by the Automotive Corrosion and Protection Committee of the International Society of Automotive Engineers in a combination environment of salt spray, wet heat and dry. The temperature is 25℃, the relative humidity is 45%, and it enters the humid and hot stage for 8 hours. This method has a long drying time and is generally used for testing automotive paint products.

4.PV 1210

PV1210-P VW is the standard for cyclic salt spray corrosion of body and accessories of Volkswagen, which is one of the most widely used cyclic corrosion test standards. The ambient temperature (25 ℃, 50%Rh) of neutral salt spray (50 × 5) g/L NaCl salt solution is carried out by this test method without drying stage. Suitable for corrosion detection of coated body, body sheet, structural components and other test samples.

JOEO salt spray test chamber

JOEO offers standard models and temperature and humidity composite models of salt spray test chamber, which can perform traditional salt spray, dry and wet alternating salt spray and automotive cyclic corrosion test, meet the requirements of salt spray control, relative humidity, air dryness, condensation humidity, automatic spray, salt water immersion, rotary spray, low temperature drying, etc. If you want to learn more about salt spray test solutions, You can contact us directly online, or send an email to: [email protected], and our team of technical experts will get you answers as soon as possible.