How do I check the corrosivity of my salt spray enclosure?

Corrosivity test according to ISO 9227 - BS aggressiveness test - NSS, ASS and CASS.

When carrying out a salt spray test according to ISO 9227, several parameters are adjusted and checked:

• the nature and concentration of the saline solution,
• its pH,
• the amount of saline solution collected (condensate),
• room temperature
• saturator temperature
• compressed air pressure

To qualify the reproducibility and repeatability of a BS enclosure, the ISO 9227 standard describes an aggressiveness test (corrosivity test).

This test allows you to know the corrosive power of your enclosure: it is recommended to conduct it every 3 months.

The procedure is described in the standard for both the Neutral BS test (NSS), the Acetic BS test (ASS) and the Cupro-acetic BS test (CASS).

This involves using six corrosion coupons (reference test panels or even reference samples), the specifications of which are:

• CR 4 steel (according to ISO 3574),
• Matte finish (Ra = 0.8 +/- 0.3 um)
• Dimensions 150x70 mm and 'thickness 1 +/- 0.2 mm.

LABOMAT offers you Q-Lab corrosion coupons, compliant with ISO 9227, with certificate, under the reference CXD-2.76-5.90-K (box of 30 coupons, divided into 5 bags of 6 coupons).

Below is the procedure to follow to conduct the corrosivity test:

• Clean each corrosion coupon (test panel) using an organic solvent.
• Weigh each coupon to +/- 1 mg.
• Fully mask one of the two sides using an adhesive as well as the 4 edges of the test panel
• Distribute the 6 coupons in the exposure area of your BS speaker, unmasked side up, with an exposure angle of 20 +/- 5 °.
• Perform a BS ISO 9227 test for 48 h.
• Remove each coupon from the enclosure, peel off the adhesive from the back side.
• Remove all corrosion products from the exposed surface by chemical and mechanical cleaning. For chemical cleaning, a solution is recommended: 20 % of ammonium citrate in water for 10 mins. Then rinse with ethanol and then with water. Dry.
• Weigh each coupon +/- 1 mg again.
• Divide the loss in mass by the area of the coupon to obtain a loss in weight per unit area (mg / m²).

Note: Corrosion products can also be cleaned using a solution described in ISO 8407: 50% HCL in water + 3.5 g / L of hexamethylene tetramine.

Your corrosion enclosure will be declared compliant with ISO 9227 NSS (neutral salt mist) if the mass loss of each corrosivity coupon is 70 +/- 20 g / m² after 48 hours of BS ISO 9227 NSS.

Your corrosion enclosure will be declared compliant with ISO 9227 ASS (Acetic Acetic Salt Spray) if the mass loss of each corrosivity coupon is 40 +/- 10 g / m² after 24 hours of BS ISO 9227 ASS.

Your corrosion enclosure will be declared compliant with ISO 9227 CASS (cupro-acetic salt mist) if the mass loss of each corrosivity coupon is 55 +/- 15 m / m² after 24 hours of BS ISO 9227 CASS. Note: There are also corrosion coupons conforming to ASTM B117 (Reference CXC-35-K).