Primary hazardous ingredients—hydrofluoric acid (HF) or ammonium bifluoride, (ABF)
Hydrofluoric acid, while an extremely hazardous material, is used in coil cleaners to etch and brighten aluminum. The etching of the aluminum removes contaminants by removal of the substrate under the contamination. This process creates hydrogen gas which is entrapped by the detergents in the cleaner forming a foam that increases surface contact time on vertical surfaces, as well as pushing contamination outward from the center of the coil. It is a very effective method of cleaning and is widely used.
Some companies have formulated so-called safer acid cleaners by substituting HF with ABF. ABF, in its raw material powder form, has a slightly lower hazardous profile than HF. The problem is that as soon as ABF is dissolved in water, it becomes HF and ammonium fluoride (AF). Therefore, any cleaner containing either HF or ABF should be handled and treated with the same precaution as an HF acid-based product. Ultimately, formulations containing ABF are no safer than formulations containing HF and should include the same safety precautions requiring specialized first aid and medical care to neutralize the effect of fluoride in the body.
These types of products should never be used indoors to clean an evaporator or chilled water coil. They should be used and labeled only as an air-cooled condenser cleaners for outdoor use.
Primary hazardous ingredients—potassium or sodium hydroxide.
Potassium or sodium hydroxide are widely used as active ingredients in coil cleaners. They clean by the same etching and hydrogen gas production method listed above for acid cleaning.
Although they do not brighten aluminum quite as well as HF or ABF, they are safer to personnel because they don’t require specialized first aid for exposure. In heavy concentrations, either of these materials will produce hydrogen gas when in contact with aluminum forming thick foam. Alkalines are generally more effective in removing greasy contamination than are acids. In heavy concentration, alkalines can be used on severely contaminated air-cooled condensers to clean, create foam, and brighten aluminum much the same as the acid based products.
In a highly diluted form, these materials can be used for light duty cleaning to increase alkalinity (pH) of cleaning solutions. At high dilution, there will be no etching of aluminum and, therefore, no hydrogen gas and no foaming action. Of the two alkaline hydroxides listed above, potassium and sodium, sodium is the cheapest but it is also the least soluble, therefore, potassium hydroxide is the best choice for use in coil cleaner. Being more soluble, potassium hydroxide rinses off coils much easier, reducing the possibility of equipment damage.
To sum up the preceding:
- All of the above ingredients function somewhat similar in use on aluminum finned coils. In high concentration, the HF or ABF acid products etch the coil, producing gas and foam. In high concentration, the alkaline product etches the coil, producing gas and foam.
In a highly diluted form, the acid products lose effectiveness (not enough acid to etch metal and create gas). In highly diluted form the alkaline product will not etch metal and produce gas, but it will increase pH of the cleaning solution resulting in quick cleaning action.
- Cleaners containing HF, ABF, sodium or potassium hydroxide are for cleaning air-cooled condensers only, outdoors.
- Cleaner containing either potassium hydroxide or sodium hydroxide:
- Heavy-Duty Cleaning: High concentrations that produce reactive, expanding foaming action from etching and gas release.
- Light Duty Cleaning: Dilute concentrations that do not etch and produce hydrogen gas.
- Acid and Alkaline cleaners should always be completely rinsed after application.
- Bad things happen when either of these two types of products are used on evaporators, indoors (etching and hydrogen gas release):
- Hydrogen gas is flammable – explosive in closed-up areas like an air handling unit.
- Hydrogen gas created by either product is highly corrosive and will possibly get into air-conditioned space via ductwork.
- The etching process will cause normal condensate flow patterns to be destroyed, in some cases causing condensate carryover and bacterial fouling in ductwork.
Failure to thoroughly rinse either of these products will result in serious equipment damage. They’re not recommended for evaporator use because it’s difficult in most installations to thoroughly rinse an evaporator. If either of these types of products are applied and the evaporator is not thoroughly rinsed, the evaporator will do its job and remove the moisture (i.e., water) from the cleaner and further concentrate the corrosive ingredient to the point it will cause pitting, electrolytic corrosion, and possibly complete coil failure.
It is important to always rinse any coil cleaner that contains acid, potassium hydroxide or sodium hydroxide.
Evaporator cleaners should not etch aluminum or produce hydrogen gas (foam). Instead they should be non-corrosive, as non-toxic as possible, and not contain ingredients that could cause system deterioration or toxic or noxious odors in air-conditioned space.
An evaporator cleaner is designed to penetrate and emulsify contaminants, thereby making them water soluble so that either rinsing or condensation will remove them from the coil. Our products utilize pH builders and corrosion inhibitors, as well as surfactants and non-toxic solvents to accomplish the job. They are virtually odorless, do not produce flammable hydrogen gas, will not etch aluminum, and yet clean very well.
The cleaning problems on evaporators are completely different from those on air-cooled condensers. Evaporators run cold, condensers run hot. Evaporators produce condensation, condensers do not. Evaporators supply indoor air, condensers do not.
As indicated above it is important to differentiate between evaporators and condensers. To grab a bottle of “coil cleaner” and use it on both can cause problems. Evaporator cleaners are not very effective on air-cooled condensers as the contamination is, in effect, baked on. Conversely, using an air-cooled condenser cleaner on an evaporator is roughly equivalent to using oven cleaner to wash your car.