101 Cleaning Zinc Alloy Fuel Bodies
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Cleaning Zinc Alloy Fuel Bodies By Bruce Smith 101 Cincae the inventrion of thbe carbureto r in Csubstitutinhg the Gereman kupfemr for copper. iworsst case sctenario rfor a cayrburetor is to re - the late nineteenth and early twentieth There are various standard formulations and Eu - plenish the gasoline in the float bowl after it Scenturies (when Zenith, Pallas, Pier - ropean casting ZAMAK has a zinc content of evaporates, ensuring a good supply of water sat - burg, and SOLEX were pioneering designs), about 95% with 4% aluminum and 1% copper. urated fuel. Carried out over several years, this there has been a need to clean the residues and Most inorganic reactions are based on this zinc sets up the ideal conditions to maximize zinc re - reactants that accumulate during use. The crud content, which can form deposits and lead to actions. The preventative solutions are to en - that forms in and on carburetors and fuel pumps corrosion damage. Extreme examples result in sure that only fresh gas is in the fuel system and generally falls into two categories: organic (from internal corrosion sufficient enough to damage that the carburetor and fuel pump are run dry petroleum residues, grease and oil) and inor - a casting beyond repair. before storing. ganic (from metal reactants, minerals and A bit of chemistry background is useful to salts). Most of these contaminants can plug jets, understand the processes that occur. Zinc is re - Cleaning Organic & Inorganic Contaminants nozzles, and pathways, preventing proper me - sistant to corrosion if kept reasonably dry. A thin So cleaning an old Zenith or SOLEX carbu - chanical operation. Some can also corrode and layer of zinc oxide naturally forms on the metal retor or a Pierburg fuel pump involves removing degrade the integrity of internal components. surface and will protect it from further corro - both organic deposits and inorganic byproducts. When a car is used on a regular basis, cycling sion. In wet conditions, a white porous residue Methods can be mechanical or chemical and fresh gas through the fuel system, most buildup of zinc carbonate, zinc hydroxide and zinc oxide need to do as little harm as possible. Mechani - will be associated with organic compounds. Re - will form, consuming the zinc and leading to vol - cal cleaning sufficient to reach all surfaces might actions with gasoline, oil and atmospheric con - ume expansion of the residue by a up to 100X. suggest abrasive blasting. This however is a very taminants result in hydrocarbon residues of But zinc corrosion may be less an issue on the bad idea not only from the standpoint of physical various mysterious forms. The exact composi - outside of a carburetor than on the inside. The damage but, more importantly, from the media tion of this gum isn’t really important as long question is how these reactions can take place left behind that will eventually damage more that combative weapons are available. Early cleaners within a closed fuel system. Under ideal condi - just the fuel system. Soda blasting may be more and degreasers were based on chlorinated hy - tions, refined petroleum will not attack zinc. If viable since sodium bicarbonate is water soluble drocarbons like carbon tetrachloride, used fuel contains sufficient amounts of water or and can be washed away, but special equipment since about 1900 as a highly effective solvent. acidic compounds, reactions will occur to form is needed and the cleaning of cavities and pas - Methylene chloride (aka dichloro-methane) was corrosive byproducts. This can be accelerated sages can be difficult. Spray and ultrasonic introduced around 1940 and has been the key with other contaminants like sulfates and chlo - cleaning are other forms of mechanical clean - ingredient in carburetor cleaners until recently. rides. ing. Spray cleaning is common in large parts These chlorinated solvents pose serious health cleaning operations, which use dedicated equip - and environmental risks and have been phased Water Effects ment and an immersion tank. Spray pressures out of consumer products over the past 30 Water content in gasoline is always a hot from 20 up to several hundred psi are used, years. Carb cleaners now contain less effective topic. With the introduction of oxygenated fuels often assisted with heat. Heated ultrasonic clean - but safer solvents like acetone, toluene, and al - and ethanol blended gasoline, concerns of water ing is also an effective mechanical approach and cohol. Methylene chloride is still available and in fuel have increased. Since alcohol and water can clean difficult to remove insoluble contam - can be found if looked for. But people die every readily dissolve in each other, the ethanol added inants. Small parts ultrasonic cleaners are avail - year from its improper handling. Using a safer to gasoline will carry water along with it. An able for occasional home use but heavy use or alternative is probably a good idea. ethanol fuel mixture can have up to 0.5% water large parts require industrial grade equipment. before phase separation (at 70°F) compared to Mechanical soda blasting, spray cleaning, and Inorganic Residue in Old Fuel Bodies 0.02% for pure gasoline. But even the water in ultrasonic cleaning are all available for small Solvent-type cleaners do little or nothing pure gasoline can pose problems when the fuel parts operation but aren’t really necessary to regarding the inorganic stuff found in a carbu - is left open to the atmosphere for long periods achieve thorough cleaning of most ZAMAK fuel retor or fuel pump. Although less of a concern of time. For instance, at a temperature of 100 parts. in daily drivers, these residues are quite com - °F, pure gasoline will reach water saturation in For chemical cleaning to be successful it mon in older cars that have been idle for some 200 days. In the float bowl of an open ZAMAK needs to remove all contaminants without harm - period of time. Many of these cars’ carburetors carburetor left filled with gasoline, this assures ing the part being cleaned. Chemicals should and fuel pumps can have scale, flakes, crust or a constant supply of water (albeit at low level) also be safe to handle and easily disposed of. powder in the float or fuel bowl. Knowing the for chemical reactions with zinc to take place. Chemical cleaning using hydrocarbon solvents composition of this inorganic contamination is Since the gasoline and water starve the reaction may work for organic contaminants, but new more important in order to understand its origin of free oxygen, a protective zinc oxide layer is formulations are lacking the necessary strength and find an effective way to eradicate it. prevented and corrosive compounds will form. to do an adequate job. An alternative approach The composition of much of the inorganic The situation will be worse when ethanol is in - is the use of less hazardous degreasers, deter - residues that accumulate in a fuel body is unique volved. Contaminants in the fuel and the atmos - gents, surfactants and acidic or alkaline-based to pot metal. The main component of our car - phere will also accelerate the problem. Fuel left chemicals to attack organic and inorganic buretors and fuel pumps is zinc, alloyed with for a long period in a gas tank will go through buildup separately. The challenge is to find the aluminum, magnesium, and copper. The the same process, ensuring ideal conditions for right chemicals and an approach that will lead acronym ZAMAK is a trade name for the alloy, corrosion in zinc fuel pump bodies as well. The to acceptable results. 68 Volume 37, Number 6 • Porsche 356 Registry Zinc is more mildly etched in organic acids, the for 12 hours or more. Halfway through the extent depending on specific chemical makeup. process and again at the end, a light brushing So the choice of cleaners and degreasers for with an old toothbrush will assist in the removal ZAMAK needs to be made with special consid - of the most stubborn dirt and deposits. Soaking eration. beyond 12 hours may yield little additional re - moval but will do no harm to ZAMAK bodies. Alkali and Acid Degreasers / Cleaners Rinsing is important and a 20 minute warm Many cleaners and degreasers are com - water rinse will remove the residual degreaser. mercially available. Among these are trade - marked products like Simple Green, Greased Step 2 – Acid cleaner. The acidic nature Lightning and Pine Sol. Chemically, there is little of Pine Sol works in two ways. It will dissolve in common between these cleaners, as their for - the inorganic residue and produce a lightly ad - mulas and pH values show: hered zinc oxide surface layer. A full strength Pine Sol soak for 2 hours at room temperature Simple Green pH = 9.5 is sufficient and safe. A slow foaming will occur Cleaning a Zenith 32NDIX Carburetor 2-butoxyethonal (a solvent) during soaking as hydrogen is released from the This Zenith 32NDIX carburetor exhibits a ethoxylated alcohol (a surfactant) dissolving of inorganic residue. Soft brushing heavy buildup of varnish, deposits and staining, trisodium phosphate (TSP, a degreaser) with a tooth brush mid-cycle will help and a final and has probably been inoperable for a long sodium citrate (an acidity regulator) brushing at the end will remove reactants from while. Signs of corrosion are evident inside, the surface prior to rinsing. A 20 minute rinse with possible damage to internal cavities of the Greased Lightning pH = 12.8 should be followed by thorough drying of the zinc body. Although a chlorinated solvent would dipropylene glycol monomethyl ether (solvent) parts and passages with compressed air. probably clean the outside of ZAMAK surfaces, dodecyclobenzene sulphonic acid (a surfactant) Following these steps, a Zenith carburetor it would leave much of the internal residue be - sodium hydroxide (a base) body will look as shown below.