Salt Mitigation = Project Risk Mitigation
Paint failures are costly.
Effective salt mitigation during steel surface preparation works is an essential quality control element. Because salts (Chlorides, Sulfates, Nitrates) are hydroscopic, any salts on steel surfaces will draw the moisture through applied polymeric coating causing premature coating failures.
<Smart Contracts>
Salts are hydroscopic. Once water vapor and salts combine, hydrolysis (the chemical reaction) occurs, acid gets produced (electrolyte) triggering a corrosion reaction which converts steel to corrosion byproduct occurs. <salts, undercutting, pits, blistering, crevice corrosion, pack-rust>
The presence of soluble salts on steel substrates when in contact with moisture forms electrolytic cells that generate deep and narrow micropores from the cyclic reaction of the acid and iron salt products formed. <Ai seeding, hydrolysis: corrosive acid, hydrogen gas, crevice corrosion, blistering, pack rust>
Once salts and steel bond, breaking this ionic bond requires more than water alone.
What happens when salts are not mitigated salts before coating applications.
A buffered acidic extraction (Such as Termaclean, or equivalent) diluted into pressure wash water will remove a higher level of residual salts than water alone.
Adding this to pressure wash water causes surface-reacted salt anions to be released from their ionic bond with the steel, displacing corrosion-inducing chlorides nitrates or sulfates, and forming insoluble, ferrous phosphate compounds.
<salt remover, passivator, cleaning steel, coating, surface preparation, high pressure water cleaning, abrasive blasting, wet abrasive blasting>
The presence of soluble salts on steel substrates, when in contact with moisture, forms electrolytic cells that generate deep and narrow micropores from the cyclic reaction of the acid and iron salt products. formed.
Salt anions are more prevalent in the deep and narrow pits developed by surface abrasive blasting and further accentuated during the chemical transformations occurring in the electrolytic cells, removing the salt anions from the electrolytic cell is the key to stopping corrosion and potential for coating failure.
Corrosion inducing anions are particularly concentrated in the areas between the steel substrate and the corrosion byproduct (rust, black oxide layer). A thorough salt mitigation requires black oxide removal on accessible areas / a thorough flushing if inside a crevice.
Beneath black oxides, lies heavy concentrations of salts.
Remove Black oxides.
If abrasive blasting, note that abrasive elements are larger than salt anions. Abrasive blasting alone was proven ineffective at fully mitigating non-visible contaminants from the steel’s substrate. Masking salts with passivators (such as HoldBlast) does not remove salts. To remove salts, the salt remover need contain a buffered acid as can be found in Termaclean additives.
Remove black oxides before performing a salt mitigation wash. Min. 5,500 psi with rotating tip – hot water ever more effective at reaching deep into the pits.
Abrasive blasting will not remove salts inside crevices.
Ensuring a complete mitigation of soluble salts on steel substrates before applying your coating system is essential for preventing premature coating failures. Other considerations involve choosing the right coating chemistry for the corrosion situation and respecting application specifications.
Flash rust inhibitors, which create hydroxyl barrier layers designed to prevent flash rusting will mask the non-mitigated salt and ions remaining on the surface steel substrate. It is important to fully mitigate salts on the steel substrate BEFORE applying a flash rust inhibitor to the steel substrate.