Why Soluble Corrosion Salts Cause Paint Failures In Steel

Protective paint coatings are the main line of defense against the corrosion of steel. Too often, however, the coating fails prematurely. Despite promising a long-term solution to the problem of corrosion, this simply accelerates when the protective coating’s life proves to be shorter than initially promised. Most failures of protective coatings occur as a result of soluble corrosion salts.

In recent years, the long-term effects of soluble corrosion salts on steel coatings have been more accurately understood. Soluble salts that remain on a steel substrate are the principal cause of premature coating failure, but they are difficult to spot because they are virtually invisible to the naked eye.

If the salt particles are not removed before the coating is applied, the consequences can be serious in the short-term, including blistering and bubbling of the paint, poor adhesion with the substrate, or corrosion of the metalwork underneath the coating.

The Damaging Effects Of Soluble Salts

Although corrosion salts are described as ‘soluble’, the fact is that they aren’t as soluble as you might expect – otherwise, they would be easily removed from a steel substrate by washing. Furthermore, as they are nearly invisible, the only way to detect them is through costly testing – and, if soluble salts are found on the substrate, they will still need to be removed before the coating can begin.

If left unchecked, soluble salts can undermine the effectiveness of the protective paint coating, in one or more of the following ways:

• Salts absorb and retain moisture from the surrounding air and, through a process of osmosis, draw the water through the protective coating.
• They increase the conductivity of the electrolyte in the corrosion cell, reducing resistance to corrosion.
• Salts reduce pH levels, as a result of oxygen permeating the paint coating; iron salts then release hydrochloric acid with a low pH level, which destroys the steel.

Whether only one of these scenarios occurs, or more than one concurrently, the effect is the same: the paint coating fails to offer the protection that it should, and premature corrosion of the steel substrate is likely.

System 918: The Solution To The Problem Of Soluble Corrosion Salts

Invented, developed and supplied by KUE Engineering, System 918 is a highly effective method for removing soluble corrosion salts from white metals or individual coats of paint.

System 918 uses an inhibited variable low-pressure wet abrasive blasting technique, with the unique ability to control water and abrasive volumes as well as air pressure.

The result? Exceptional results that eliminate the risk of corrosion forming beneath the protective paint layer, extending the life of the steel, and avoiding unnecessary costs to rectify the damage. For more information about KUE Group’s System 918 and to discover how it could protect the protective coatings of your plant or equipment, please get in touch.