Frequently Asked Questions
Q. Is it possible to retrieve a removed engine code?
A. After doing some research I have come to the unfortunate conclussion that they can only sometimes be retrieved. There is a mild acid test that the police use to reveal the original numbers on firearms and other filed off numbers such as engine codes. When numbers have been over-stamped or obliterated by grinding, sanding or other methods, the numbers may no longer be identifiable. Through use of chemical and physical restoration techniques, the numbers can sometimes be made readable again in some cases though. The reason the numbers can be restored with the use of acid is that the substrate directly beneath and surrounding the stamped serial number is denser than the remaining substrate. The denser metal will dissolve slower, “raising” the serial number. The method of revealing eradicated serial numbers with acid is also known as acid etching. The only problem with using acid is it only reveals the serial number for a little while until the acid eats away the rest of the metal. Another method I have read about is Ultrasonic Cavitation. This method has been applied successfully to gun parts. This method has also shown success in restoring numbers after prior failure using chemical etching techniques. The information I found about the ultrasonic method was that it was not successful on a heavily obliterated and restamped automobile engine block, but it was partially successful on a motorcycle gear-case housing.
Everyone asks what acid is used to reveal erased engine codes. This seems to be a very highly kept secret in the law inforcement community. Well, after searching the internet for hours the only thing I have come up with is an article from someone in Kelantan, Malaysia that tested different solutions. As I have not tried this and am not an expert on this by any means please take this for what it's worth. By no means do I want anyone to try this on an engine block unless you completely understand what it could do to your block which worst case would be destroy it. Also acid is very dangerous so please take every precaution possible to protect yourself and others from harm. That was my word of warning on the folloing information. Anyway, the tester from Malaysia determined that while most of the solutions that were tested were able to restore marks up to certain levels of erasure, the solution 5g copper sulphate, 60ml water, 30ml concentrated ammonium hydroxide and 60ml concentrated hydrochloric acid restored marks erased to a depth of 0.04mm below the depth, thus presenting itself the most sensitive solution. Another solution I have read about for etching steel is 50% hydrochloric acid with 5 gms. of cupric ammonium chloride added for each 100 ml. of solution. This solution is stable and may be kept indefinitely in glass containers with glass stoppers. To prepare 50% hydrochloric acid add one volume of concentrated hydrochloric acid to an equal volume of water. Always add acid to water never add water to acid. The etching solution may be applied with a cotton swab attached to a glass rod or a wooden stick. The etching can apparently be speeded up, and sometimes better definition can be obtained, if an electric current is permitted to flow through the etching fluid. An ordinary flashlight battery may be used to supply the electrical current. For better results from using the acid etching method you should remove scratches. Remove only enough metal to eliminate the scratches though. Remember the more level, smooth, and even highly polished and mirror-like the surface is the more successful the restoration will be. Remember that using acid may reveal the stamped number for only a brief moment so have a camara ready just in case.