Tags: #architecture #buildingdesign #buildingscience #materialsscience #mgo #researchanddevelopment #waterresistance

Sometimes less is more. A 7-day immersion test can be reduced to 24 hours with the right substrate. 

Immersion methods outlined by AAMA 711/714 are often embraced by WRB systems. The 7-day immersion and peel test sounds arduous, and to many products they are. But where AAMA sees the value of anodized aluminum, those evaluating WRBs should be concerned with alternative substrates. Porous substrates. Substrates that get wet or even fully saturated beneath the coating and/or applied liquid flashing. 

Peel adhesion testing may result in removed coating, removed sealant/flashing, or both. And testing sealants or liquid flashing on uncoated specimens can offer even further insight (think joints).

Substrate-specific testing is always preferred. This gets tricky for certain substrates such as glass mat gypsum, which can disintegrate under prolonged wetting. Other substrates such as wood, concrete, and MgO are more suitable. MgO is particularly useful as it is porous, convenient, and dimensionally stable in water. 

This 24-hr, substrate-specific test has been critical in my efforts for screening coating formulations intended for partial or full immersion. A go-to for fast-tracking R&D efforts.

Within the first hour of posting this, I’ve received several private messages. The central theme: “Should MgO be integrated into standard water immersion testing?” My opinion – yes, it should. It makes for a perfect analog for many porous substrates while remaining dimensionally stable, cohesive, and predictable in its coated interface behavior.

Warning – few coatings pass this rigor. But if you are looking for a method to improve your coating’s performance, it offers an interesting and insightful benchmark.

Other than peel testing of coatings and sealants/flashings, I also use this method to examine the effects of cure times, abrasion resistance, and immersion cycling.