Salt spray test test method-can be used for aluminum corrosion test(2)

Evaluation of salt spray test results

The result evaluation methods of the salt spray test include: grading method, corrosive appearance evaluation method, and weighing method.

Grading method

The percentage of the ratio of the corrosion product to the total product is divided into several levels according to a certain method, and a certain level is used as the basis for qualification judgment, which is suitable for evaluation of flat samples. Such as GB/T6461-2002, ISO 10289-2001, ASTM B 537-70(2013), ASTM D 1654-2005 all use this method to evaluate the salt spray test results.

RP—protection rating value;

RA—appearance rating value;

A—When calculating RP, it is the percentage of the corrosion part of the base metal to the total area; when calculating RA, it is the percentage of the corrosion part of the protective layer to the total area.

The representation method of protection rating is: RA/—

For example, when the slight rust exceeds 1% of the surface and less than 2.5% of the surface, it is expressed as: 5/—

The expression method of appearance rating is: —/RA value + subjective evaluation + cover layer damage level

Such as: Moderate spots, with an area of more than 20%, expressed as: —/2mA

The expression method of performance rating is: RA value + subjective evaluation + cover damage level

For example, the sample does not show corrosion of the base metal, but there is slight corrosion of the anode coating layer less than 1% of the total area, which is expressed as 10/6sC

Corrosive appearance evaluation method

It is a qualitative determination method. It determines whether the product corrodes after the salt spray corrosion test. Such as JB4159-1999, GJB4.11-1983, GB/T4288-2003 use this method to evaluate the salt spray test results.

Weighing method

It is a method of weighing the weight of the sample before and after the corrosion test to calculate the weight of the corrosion loss to evaluate the corrosion resistance of the sample. It is especially suitable for assessing the corrosion resistance of a certain metal.

V loss—metal corrosion rate, g/m2·h;

m0 — mass of the test piece before corrosion, g;

m1 — mass of the test piece before corrosion, g;

S — the area of the test piece, m2;

t — the corrosion time of the test piece, h.