Acidic cleaning agents are preferred for cleaning applications which involve the removal of oxides, scale, rust, and other difficult-to-remove contamination found in many industries.  However, using acids in ultrasonic cleaners can create many problems with regards to the reliability of the ultrasonic cleaning system and flash-rusting of parts.

Problems with Acidic Reformulation

While the acids in use could be perfectly compatible with the 316L material of construction of an ultrasonic tank, there are times when the contaminants being removed contain chlorides, fluorides, or bromides.  When this is the case, the acids re-formulate into OTHER acids which are NOT compatible with the tank.  For example, a safe phosphoric acid cleaning agent would turn into hydrochloric acid or hydrofluoric acid, both of which will cause crevice or stress corrosion cracking.  Therefore, one must be very sure that the contaminants or parts do not have these substances on them.

Problems with “Flash Rusting”

In most cases, the parts being cleaned with acids are made of steel. When steel is cleaned in an acidic cleaning fluid, the surface is microscopically etched away, leaving clean bare metal which is significantly more prone to flash rusting than it would be if cleaned in an alkaline cleaning fluid. While rust preventatives can be used to prevent after-cleaning oxidation, care must be taken to ensure that the concentration of any aqueous rust preventatives is adequate, and in most cases this concentration must be higher than it would have been if the parts were cleaned in an alkaline cleaning agent.

Problems with Temperatures & Concentrations

Acidic cleaning agents are very sensitive to temperatures and concentration levels, much more so than alkaline cleaning agents.  For every 7 degree temperature increase in an acid cleaner, the aggressiveness of the cleaning agent doubles.  Therefore, bath maintenance becomes a much larger challenge than when using alkaline cleaning agents.  Operators must ensure that the concentration and temperature of the acidic cleaning agent is perfectly maintained.

Problems with Selecting the Appropriate Cleaners

While Zenith can provide recommendations for acidic cleaners which have worked successfully for years in an ultrasonic cleaning environment, many customers change cleaning agents without contacting us with highly destructive results.  One of Zenith’s customers found an acidic cleaner that worked perfectly for their application only to find pinholes in the tank after a few months of operation.  The acid chosen was said to be compatible with stainless steel and stainless was recommended as a storage container by the manufacturer.  The problem was that ultrasonic cavitation super-heated the acid at a microscopic scale, making it significantly more aggressive and no longer compatible with the material of construction of the tank.  The SDS sheet did not have a single hazardous ingredient listed and operators claimed that it did not create itching or irritation when exposed to the skin.  It also had a sweet non-acidic odor.  It appeared to be the perfect cleaning agent until the moment that the tank was completely destroyed and required replacement.

Use Zenith’s Recommendations

If an acidic cleaning agent is required to obtain the desired cleaning results, make sure to contact Zenith for assistance in selecting the appropriate cleaning agents.  We have been in business longer than any ultrasonic equipment vendor in the USA and have the experience required to recommend the perfect cleaning agents for your application