Using vitamin C or ascorbic acid as corrosion inhibitor has several weakness. In its liquid form ascorbic acid is easily oxidized and its anti oxidant properties unstable due to heat, light, oxidizer, dissolved oxygen and heavy metals. Purple sweet potato (ipomoea batatas L) with its high anthocyanin is one of alternative for green corrosion inhibitor. Extract of purple sweet potato has the ability to hold the enzyme reaction and oxidation proses of ascorbic acid. Purple sweet potato extract mixed with ascorbid acid is used as inhibitor of API 5L steel in 3.5%NaCl. This compound is classifid as mixed type inhibitor. The adding of purple sweet potato extract will assist ascorbic acid to maintance its inhibition efficiency and increases surface layer corrosion resistant of steel. Polarization methods and electrocehmical impedance spectroscopy (EIS) are used to investigate corrosion rate and mechanism of the steel. Appliaction of 4 ml purple sweet potato mixed with 10-4M ascorbic acid inhibitor increases inhibition ability of API 5L steel from 23.5 to 57.52%. Purple sweet potato extract moves polarization curve to lower potential (below 82 mVolt) with tends to be more negative.

Utilization of ascorbic acid as corrosion inhibitor has several weaknesses. These weaknesses are easy to oxidize in solution form and reduction of its antioxidant properties due to heat, light, oxidizing agent, dissolve oxygen, and heavy metals. Purple sweet potato extract is an alternative green corrosion inhibitor with major contains of anthocyanin compound. Anthocyanin will withstand enzymatic reaction and oxidation process of ascorbic acid. Addition of purple sweet potato extract in ascorbic acid will enhance inhibition efficiency of steel compare to the used of ascorbic acid alone. Interaction of purple sweet potato extract with 0.01M ascorbic acid in 0.1M FeCl3environment was analyzed using FTIR spectroscopy. The result shows that interaction of purple sweet potato extract with ascorbic acid in 0.1M FeCl3build ability to form iron chelate.

In pipeline constructions especially for oil and gas, corrosion is a natural phenomenon which cannot be avoided but can be reduced. There are many kinds of corrosion protection can be used in this area and inhibition is one of it. At present inhibitors used commonly from chemical kind. This kind of inhibitor is expansive and toxic. The knowledge of plant substances have opened a new era of inhibitors. Research has proved that inhibitor can be made from plants which are rich in antioxidant and tannin. This research is conducted to see the inhibition mechanism of several plants which are rich in antioxidant and tannin. The plants used as inhibitors in this research are: manikara zapota; garcinia mangostana l., and ipomea batatas. Corrosion test are applied to API-5L in produce water environment. The conclusions of this research show that it is possible to use plants as inhibitor and when it is used as inhibitor every plant has their own mechanism.

This article describes an experimental study of the effect of using sawdust as a mixture of concrete pipe on water absorption and compressive strength. This research was inspired by the amount of sawdust waste from sawmills that had not been utilized. For this purpose, 18 specimens were made with four different values for sawdust: iron ore (5%, 10%, 15%, and 20%). Each specimen has the composition of cement: iron ore (1: 4), and water: cement (0.5%). This research was conducted at PT Indal Steel Pipe. This research to analyse the effect of using sawdust as a mixture of concrete pipe on water absorption and compressive strength. Experimental method using compression test and water absorption test has been used to this study. Main finding from this study showed the higher the composition of sawdust increased water absorption and reduced the compressive strength of the concrete pipe. This study will be useful to reduce waste pollution and improved concrete pipe material in term of production cost.